First off, my review concerns my point of view. Perhaps you are not interested in the same things as me so keep that in mind.
I like to cruise on ships that have plenty of space up top. For instance, I have cruised with Royal Caribbean many times. Their top deck is un-matched. I have found all ships to have a running track around the top deck. Plenty of space to spread out and enjoy the seas.
I like pools. I like to lounge in chairs and get in the pool. Keep in mind the Epic is the only NCL ship I have been on. The pools were small, filled with kids and the water looked .... well, you get the idea. I wouldn't want to get in.
I stayed in a solo cabin and it was fabulous. Quiet. So relaxing. I slept like a baby. I don't need a balcony or sliding windows, I'm seldom in the room and since we were at sea only one day, why spend the money?