I guess I'm the oddball here but we really will only cruise with
DCL anymore. We've cruised on Carnival 3x, never wanting to spend the extra $ on DCL. At the time I figured if we want to see Disney characters, we'll go to WDW. Boy was I wrong. We fell in love.
The Magic is such a beautiful ship, very tastefully decorated, unlike the neon and so much fuschia we saw on Carnival; looked like a wh*r*house. Also everything from buffet trays to evening shows, are created with families in mind. I've never needed to ask if a show was appropriate for children, and yet my dad, in his 60s loved it so much, he even went to the last night's show alone while my mom and I packed. There is so much to do, we couldn't fit it all in on a 7 nt cruise and even after 3 7-nt DCL cruises now, we still haven't done it all.
After our 1st 2 DCL cruises we tried 2 RC cruises, first was adults only with friends, for dh's big birthday. We had a great time but more b/c of the friends we were traveling with. The whole cruise seemed to focus on drinking and gambling. Someone vomited in one pool so it had to be closed. Another young guy was literally falling down drunk poolside til his friends carried him off. Granted it was a short cruise, 4nts, during spring break so it tends to attract this type of crowd.
We gave RC another chance last June (and with kids) sailing to Bermuda, where DCL doesn't go anyway. People were not so drunk but boy they really push the drinks while sitting poolside. I must have told him no about 6 times. Also there is a lot more smoking overall compared to DCL. Sometimes to get from one part to another, you must cut throught the casino which is very smoky. We ended up going up another flight to avoid it.
Also annoying was how you have to sign out a pool towel and if it's not returned to the deck 11 desk, you are charged $20 per towel.

I spent half the cruise nagging my kids about the location of their towels as I didn't want to be stuck with a $40 missing towel bill. Carnival was the same way but my kids were much younger then (4,7) so I had been carrying their towels anyway and there was no independence for them back then.
When returning from a beach with wet towels, you have to trek back up to deck 11 to return them; DCL has a huge towel bin at the gangway, so you dont' even have to carry them back onto the ship. Much more family friendly imo.
My kids enjoyed the ice skating and rock climbing wall, the rare times it was even open. We're not into the hairy chest contests, sexy leg contests, etc that we saw on RC and Carnival.
My kids were never into the kids clubs on any ship but once my older ds could go to Ocean Quest, he loved it and now is looking forward to going to the Stack as a teen.
We all agreed that DCL fits us like a glove.

We get our Disney fix and cruise all in one.
ymmv
Check out the cruise boards here on the Disboards; very friendly crowd.
http://www.disboards.com/forumdisplay.php?f=9