We've been on three NCL cruises and have our fourth coming up next month. Up until this cruise on the Joy, ours have always been on the smaller ships, so I can only speak to that experience for now. However, for what it's worth, we love NCL.
The positives as compared to
DCL:
We find the service comparable to DCL, though maybe a bit more subtle if you know what I mean. We don't really like to be fawned over and sometimes DCL can be a little bit much - but that's just us.
Food is subjective, but we very much prefer the dining experience on NCL. We like choosing when and where to eat, and we think the food overall is just better on NCL. Just make your reservations for specialty restaurants as soon as your window opens up. Having a buffet option for every meal is a big plus to me, especially on port intensive cruises. Sometimes we are just too tired to deal with going to a dining room and having a big dinner. Most of the buffet food is actually pretty good. Just avoid anything with steak in the name unless you enjoy shoe leather

.
We have always sailed in suites on NCL for close to (or even less than at times) what a DCL balcony would cost. We love that. Now, things have changed over the last few years - even before the pandemic. It used to be if you booked early you could snag a suite or the Haven at a good price. Now they price them sky high at the get go. On our upcoming cruise we booked a room we'd be satisfied with but was much cheaper than the Haven hoping to use NCL's upgrade program where you bid on upgrades in the weeks leading up to your cruise to upgrade to a Haven room. We had placed our bids a few weeks ago, but then few days ago they dropped the price pretty dramatically on a couple of categories and we were able to upgrade directly and pick our cabin for just under $1100. That cabin would have been about $5000 more 6 months ago. So watch prices, and use the bid process if you don't see a price you're comfortable with. There is no guarantee you'll win, but you do have a shot of upgrading.
You can book your shore excursions as soon as they load them in the system for your cruise. I'm not sure when that really is but have booked them at least 6 months out before. There's no booking by loyalty club level, staying up till midnight to curse a crashing website, etc. Just log on when you see something you like and book it. No fuss, no muss.
Drink packages - we enjoy adult beverages so this appeals to us. It's a turn off to some people, though.
Negatives
Entertainment is definitely geared more to adults. We are a family of adults, so we like that. Families with small kids will have a different opinion.
I miss the dedicated movie theaters on DCL. We always catch one or two on our DCL sailings.
On the larger ships you have to reserve most of the shows. This will be our first time experiencing that, but as we are in the Haven now I'm not too worried about it. If you aren't in the Haven you can make them on the app or over the TV. There may even be a desk somewhere that takes them, but I'm not sure about that.
We don't gamble, so we never use the casino. However I appreciate that gamblers are basically subsidizing our cruise fare as cruise lines that have casinos usually are much less expensive due to the revenue they bring in from them. That being said, on a lot of the ships they reek of smoke which I hate. I've read that some of the newer ships have an enclosed smoking section in the casino now, it's not so bad.
Bottom line, the Prima looks awesome. We can't wait to sail on her some day. But we are also looking forward to being back on the Magic next year. Variety is the spice of life!!