Sailed
DCL, Carnival, Celebrity, Holland America, NCL and
RCCL (But a long time ago and without kids).
NOTE: just reread everything I wrote below and I sound like I HATED my cruises, but I have never had a bad cruise, including on all these other lines, but I did compare to DCL constantly and found a lot lacking.
Celebrity would be my 2nd choice if price wasn't an option, but not on the options for the poll. Food was great and the kids enjoyed it because they were one of only a handful (literally!) of kids in September/Alaska cruise, and we used our OBC to buy a package for them that included them to be able to use the kids club all day (including weird lunch and dinner hours when it was normally closed). Entertainment sucked though, not kid friendly pretty boring. Not much to do at night but enjoy the free drink package. But overall, very much for adults, very "fancy" - not family or kid oriented outside of kids clubs, and many fellow passengers are "anti-kid" - "so glad there are no kids on board" (without knowing we had 2 kids with us). Would probably not be great during peak kid season, but ship was beautiful. First time I went was with my husband and it was very nice without kids of course. Tends to be expensive.
After that I would choose Carnival because at least it is cheap, I thought the food was good - but it has been a few years. Lots of quick dining options and very family and kid oriented.. Rooms are not great but lots of good trivia and things for kids to do. Pool and waters slides for kids. Older kid hated kids club, younger son liked it. Fellow travelers - well the only place I ever had someone admit to me they were going to remove all tips because they just couldn't afford to pay them and didn't realize they would have to. Lots of drinking in excess, especially around the pool. Entertainment - not very good but for comedians. Can definitely veer to the tacky, but certainly not pretentious.
We had a great time on HAL, but mainly because: 1) went with family; 2) played a lot of trivia; 3) lots of hot tubs, which kids loved and 4) hardly any kids so my kids got a lot of attention. But older ship (at least, what we went on), service was worst I have EVER had on a cruise; comically bad I though we were being punked for a hidden camera show (until my sister said, I cannot eat in the dining room another night like this on day 2, complained and we got a new server who was good if not very engaging like on DCL). Definitely skews older and the entertainment reflected that. Musical reviews that probably were being done on the cruises in the 70s; comedians who appeared to do the shows from the Catskills in the 50s, including racist, tasteless humor; supposedly kid friendly, but too risque for my son. Walked out. Thank god they had a library and I was with extended family, as hanging out and reading was all I really had to do at night after trivia ended. Room was tiny and as soon as we got on my son got locked in bathroom as lock was defective. Would probably only do again with fantastic itinerary - I hear they are good for Alaska.
NCL we had a great itinerary (Med cruise) but if we hadn't been in the Haven I would have been miserable (but since I WAS in Haven, I was in Heaven

). Ship is TOO big, TOO crowded and everyone has drink packages so all the bars are 3 people deep (except Haven). Other than Haven, service sucked. Non-specialty restaurants always seemed to have a wait at dinner. Didn't go outside of Haven after day 2 but for specialty restaurants. I was "registered" as GF, but literally met servers in the non-haven restaurants that did not even know what that meant. Not a problem if you are in the Haven, but the couple times we ventured out it was so NOT relaxing. Trivia sucked -worse ever of any cruise- actually complained on comment card. Entertainment was usual non-DCL cruise fare - boring, mostly not kid friendly. I have considered cruising on NCL again, but only if in Haven is affordable or REALLY excellent itinerary for a great price. But, my younger son loved the pool, slides, etc (but not the kids club- he was used to being allowed self-checkout and NCL doesn't allow it until you have been there 2 hours, and no wave phone or text to let me come get him earlier). Older son liked the teen club.
RCCL I did years ago with my husband on our honeymoon, we rarely left the cabin but for casino and when we didn't order room service, so...hard to say what I would think with kids today. Price wise they are attractive but not a fan of mega ships. I never use casinos on cruise ships anymore, btw, so used to not having them on DCL and very happy about that. No smoky rooms, no throwing money and time away on useless things on vacation.
I want to try MSC. I don't get Princess - can't figure out what kind of cruise they offer and when I look at cruises the prices are SOOO high, I stop almost immediately. Just appears boring to me, and overpriced.