We chose Hurtigruten because we wanted to see Norway's coast & spectacular scenery in detail as one part of our Norwegian holiday. We chose the Nordlys because it fit with our schedule but also because it was an "expedition" ship with more active-oriented excursions available. The scenery itself was 4-5 stars while the ship and onboard experience was 2-3.
The best part of the journey was traveling through fjords large and small as well as the number of sea days where you could simply relax while looking out a window or sitting on the rear deck as the ship worked its way along the coast while making numerous stops at small towns. We also thoroughly enjoyed the variety of excursions, especially the hiking and bicycling activities that we took part in.
For those who like lots of activities and options when traveling, the Nordlys does not fit the bill. While there were 1-2 informational sessions or narratives of the scenery each day, there was no entertainment, no music (live or recorded) in the bar or lounge, no bingo or games organized by a cruise director, no pool, no sauna (it was out of order, and also 1/3 of the gym equipment was non-functional), etc. If you like reading, playing cards or table games with friends/family, or a cruise with lots of sea days to do nothing, then Nordlys may be a good option.
The cabin itself - we were in Arctic Superior - was very small and felt equivalent to a roadside three-star motel. The bathroom is tiny, and I think some people would have trouble taking a shower. The cabin's two twin beds configured in an L shape. Hurtigruten would not provide cabin information in advance. The literature I read indicated that some Arctic Superior rooms were configured to be able to have one double bed instead. On board I asked about changing to a cabin like this but was told none of the rooms were configurable to a double bed unless I wanted a small suite for an extra $650/night. The superior cabins had no visibly superior amenities, such as premium linens, better mattresses, turndown, etc.