While Royal Caribbean's Harmony of the Seas is still the biggest ship in the world (by quite a lot), MSC Cruises' newest behemoth -- MSC Meraviglia -- has muscled itself into the number four spot, just behind Harmony's sisters, Allure of the Seas and Oasis of the Seas.

Both ships offer a dizzying array of things to divert you, whether that's water slides, games, arcades, parades, awesome kids' programming, restaurants or shows. So how do you know which ship to choose?

We pit Harmony of the Seas vs. MSC Meraviglia against each other, comparing dining, bars, cabins, activities, outdoor fun, entertainment, family offerings and itineraries to help you decide which mega-ship is the best choice for you.

Stats

At more than 170,000 tons Meraviglia is some way behind Harmony, which measures 227,500 tons. Meraviglia carries 4,475 passengers compared to Harmony's 5,479 and is 1,033 feet long compared to Harmony's 1,188 feet.

There are 1,536 crew on Meraviglia compared to 2,100 on Harmony, which gives Meraviglia a higher passenger-to-crew ratio -- 2.9 compared to 2.6 on Harmony.

Dining

Meraviglia has 11 actual sit-down restaurants; Harmony has 16. Just five of those on Meraviglia are included in the cruise price, while half are included on Harmony. Dining venues without a surcharge on both ships include one or more main dining rooms, a pool deck buffet and several quick-bite, order-at-the-counter spots. Both ships deliver a tasty array of international cuisines, but if you're keen on traditional American-style dining (think Johnny Rockets and the deli-style Park Cafe), Harmony of the Seas is a better bet.

Free Dining

Both ships offer traditional, set-seating main dining rooms (with early and late dining times), as well as a flexible option that allows passengers to choose when they want to eat.

Suite passengers on both ships have an extra perk: a suites-only restaurant. On Meraviglia this is in the Yacht Club Dining Room and on Harmony it is the Coastal Kitchen. Both restaurants are in lovely spots at the top of both ships; Meraviglia's offers lunch and dinner with a menu that changes daily; Coastal Kitchen features two Mediterranean-inspired menus that rotate throughout the cruise.

There is also a buffet on both ships: Windjammer on Harmony of the Seas and the Marketplace on Meraviglia.

All other included-in-the-price eateries on both ships are casual spots, where you order food at the counter (or browse buffet-style) and either take the food to go (Boardwalk Dog House, Vitality Cafe and Park Cafe on Harmony; Atmosphere Bar South on Meraviglia) or sit at tables inside the venue or located nearby (Sorrento's and Solarium Bistro on Harmony).

Extra-Fee Dining

When it comes to restaurants that carry an extra charge, Meraviglia has five a la carte restaurants, and one with a cover charge (not a restaurant, but Chef's Table).

Two are brand new to MSC, making their debut on Meraviglia: Butcher's Cut, an American-style steak house offering prime cuts of steak, lamb and even buffalo. And Kaito Teppanyaki, which is a 32-seat venue with a sushi bar out front. The Chef's Table is a 100 euros per person set menu.

The other for-fee spots carry small charges -- snacks in the Brass Anchor pub and crepes at the Jean-Philippe Creperie.

Harmony has five restaurants with cover charges and three where food and specialty coffees are priced a la carte. Restaurants include Jamie's Italian, molecular gastronomy in Wonderland and Chops Grille, Royal's signature steak house.

Bars

With 17 drinking establishments on Meraviglia and 14 on Harmony, you'll have no difficulty finding a spot to suit you. The bars on both ships are hopping at night with live music in many of the venues, plus promenade parties and salsa dancing in the many lounges.

Harmony's bars include a couple of gimmicky choices: Rising Tide Bar and Bionic Bar. There's nothing special about the drinks you'll find here, but the Rising Tide Bar travels vertically between three decks, and robotic arms mix your cocktails while dancing to music at the Bionic Bar. It also has a "traditional" English pub -- the Boot & Bonnet, which has a good selection of British beers (and even "beer-tinis" and "cockt-ales," which are a mix of beer and spirits).

Meraviglia eschews gimmickry for more traditional venues -- a Champagne bar, a sports bar and Edge Cocktail Bar, plus a "traditional" English pub, the Brass Anchor, with 45 different bottled beers. There's also a sophisticated lounge bar with live music, Sky Lounge.

Cabins

Both ships share basic cabin types -- standard inside (no window), ocean-view (porthole or window views) and balcony cabins -- and even a few of the suite types.

Meraviglia debuts a few cabin firsts for the line, including Duplex Suites, which bear a strong resemblance to Harmony's Sky Loft Suites. Both are double-height, with a living room on the lower level leading out onto a balcony, and the sleeping area above, looking out onto the living area. Where they differ notably is Meraviglia's Duplex Suites include a hot tub on the balcony.

They also share some technological stateroom DNA. Harmony of the Seas has inside rooms with virtual balconies, offering cruisers views of the outside world via floor-to-ceiling high-def TV screens designed to mimic the balcony experience. (You can even pipe in wave sounds.) Meraviglia also offers a virtual experience in its inside cabins, but it is just a TV-sized space, designed to mimic a window rather than a whole balcony.

Harmony also offers inside cabins with real views (though not of the ocean) -- due to the ship's structure, there are many rooms that have inside balconies and/or views. These include cabins overlooking the Boardwalk, the Promenade and Central Park.

Meraviglia debuts 13 single cabins, with the aforementioned virtual windows. Solo cruisers also will find inside studio cabins (15 of them) on Harmony of the Seas, sized and priced for one person. Twelve of these have ocean views.

As for family-specific rooms, both Meraviglia and Harmony of the Seas have lots to offer, including inside, ocean-view and balcony cabins specifically designed for families. Meraviglia debuts "Super Family Cabins," which are three connected cabins (two balcony and one inside), which can sleep up to 10 people.

Harmony also offers more than one type of family-specific suite, including the vast 1,165-square-foot Presidential Family Suite.

Suites

Meraviglia debuts the biggest Yacht Club -- the line's "ship-within-a-ship" -- in the MSC fleet. This is where the majority of suites are located (except, oddly, the Duplex Suites). Here you'll find the standard Yacht Club suites -- the 226-foot Deluxe Suites (which also include two "Wellness Suites" that have a Technogym Kinesis for working out in your room.) There are also two Royal Suites, which come in at 699 square feet and include a bedroom and separate living area, as well as a 430-square-foot balcony. The Yacht Club perks are extensive, with priority boarding, and access to a private sun deck, lounge with free drinks and dining room.

Harmony's suites are on average significantly bigger than those on Meraviglia. They start with a junior suite (287 square feet with a 78-square-foot balcony), and end with the massive, two-deck Royal Loft (1,599 square feet with an 874-square-foot balcony); in between you'll find Grand, Owner's, AquaTheater, Crown Loft and Sky Loft options, and the aforementioned family suites.

Perks-wise, it depends on your suite category, which is divided into three classes: Sea Class, Sky Class and Star Class. All Suite Class passengers get access to the Coastal Kitchen restaurant for dinner, bottled water, luxury bath products from the likes of Hermes, Ferragamo and L'Occitane (depending on the category), bathrobes and pillow-topped mattresses.

Sky Class passengers additionally get all-day access to Coastal Kitchen, in-suite dining, complimentary Voom internet access, a one-day pass to the spa's Thermal Room and concierge services. Star Suite perks include drinks, dining at the ship's specialty restaurants and access to a Royal Genie, a glorified concierge/butler.

Activities & Outdoor Fun

There is no shortage of fun on both of these mega-ships, whether indoor or outdoor, adult- or kid-oriented.

There's always a party going on, on Meraviglia it's usually on the Pool Deck. By day it's pool games, trivia and various water sports tournaments to the accompaniment of very loud music; by night it's the White Party and an open-air disco.

On Harmony, you'll find similar daytime games, but the ship is a little more sedate at night.

Both ships boast water slides -- on Meraviglia you've got the Polar Aqua Park, which includes a kids' splash area and three slides, one called the Champagne glass, which deposits you at high speed, into a bowl-like structure where you spin round and round; on Harmony, meanwhile, you've got the Perfect Storm trio of water slides: Typhoon, Cyclone and Supercell, as well as the family-friendly Splashaway Bay with smaller slides, water cannons and drenching buckets.

But it's Harmony's dry slide which has garnered the most headlines -- The Ultimate Abyss is a 10-story dry slide that drops 100 feet to the Boardwalk and is not for the faint-hearted.

Both also have a basketball court that can convert into a volleyball court or occasional soccer pitch. Both have four pools.

They also share a feature, which up until the debut of Meraviglia was unique to Royal ships: a central promenade, lined with shops, bars and restaurants, which turns into a spot for parades and parties at night. The key difference is Meraviglia's has an 80-meter-long LED ceiling that projects stunning images day and night.

On Harmony, you'll find a number of unique-to-Royal features: an ice skating rink, a Boardwalk-style arcade with classic carnival games (skee ball, ring toss, etc.), the FlowRider surf simulator, climbing walls and a zipline. Meraviglia has a ropes course above the aqua park.

Meraviglia also has an arcade with bowling, a 4D cinema, two Formula One race car simulators and a virtual flight deck.

Day and Nighttime Entertainment

The big ticket shows for Meraviglia come from Cirque du Soleil, which has created two productions exclusively for the ship (and will be rolling out more on future ships). Sonor and Viaggio are classic Cirque -- extraordinary acrobatics, wonderful visuals, booming sound and fairly plot light. Meraviglia also offers a number of more "standard" revue-type shows in the main theater.

Harmony grabbed headlines with the first ever production of Grease on a ship, and the first one that combined elements of the movie and the Broadway production. It is outstanding. Harmony also has full-scale production ice shows in the ice skating rink, two different acrobatic diving shows in the AquaTheater and as well as Grease and a full-length Broadway-style show: "Columbus, the Musical."

Meraviglia has plenty of bars and lounges, with live music in most, as well as in the Atrium. Both ships also offer karaoke in very similar spots -- on Meraviglia it's called the TV Studio; on Harmony it's called On Air. Both are along the main promenade. Harmony of the Seas also offers Jazz on 4.

Children's and Teen Programming

Both ships score high marks for their kids offering, with dedicated spaces at the top of the ship: Doremi Club on Meraviglia and Adventure Ocean on Harmony.

These huge spaces have dedicated rooms for specific age groups, as well as additional rooms such as a science lab (on both) and a family/performance room (on both).

They also cater outstandingly for babies; MSC's has a link-up with Italian babywear specialist Chicco and has no lower age limit for babies (counselors will even change nappies). Harmony offers the Royal Tots and Royal Babies Nursery, which provides interactive activities for children from 6 months to 36 months old (when accompanied by a parent), as well as extra fee drop-off babysitting services. On Meraviglia for-fee after-hours babysitting is available in the club only, on Royal Caribbean, you can also get in-cabin babysitting for a price.

MSC's partnership with LEGO means all the kids' rooms are LEGO-themed; while Royal's partnership with DreamWorks means the designs evoke some of the film company's most popular films and characters (Shrek, How to Train Your Dragon).

Teens get hangout rooms on both ships -- the Teen Club on Meraviglia, plus access to a nearby disco; and on Harmony The Lounge, which doubles as a disco.

Programing across all age groups is outstanding, with kids occupied throughout the day with sports, activities, games and educational activities.

And, of course, kids on both ships get to enjoy the splash water parks mentioned above, complete with slides, water cannons and dunk buckets.

Itineraries

Meraviglia is Mediterranean-based and offers seven-night sailings calling at Genoa, Rome, Naples, Sicily, Malta, Barcelona and Marseille. It will reposition to the Caribbean in 2019. Harmony operates out of Port Everglades, offering Bahamas and Eastern and Western Caribbean sailings, with stops at St. Thomas and Royal Caribbean's private Haitian island of Labadee.