The difference in quality of the inside staterooms is a big part of the reason why I won't go on another Carnival cruise. One was way more than enough. Our air conditioning on the carnival ship never got the room down below 76F (and often not even that low), which is not awful at home, but made the tiny room completely stifling. It felt like there was never any air flow coming into the room. At several points, I had to go out into the hallway just to feel like I wasn't suffocating. On
DCL, it was a completely comfortable temperature. On Carnival, the lights in the room were super harsh, making it really unpleasant to be in there for any length of time. On DCL, the lampshades at the headboard gave the light a comfortable, yellow glow. It was never unpleasant to be in there. The bed was super comfortable. The rooms on DCL (we were on the Magic) seemed to be much more roomy. I never felt stuck in a tiny box. Having a bathtub on the DCL cruise was a huge convenience with having a young child. The towels -- I felt like they were fine, but not having to carry towels to the pool and back and keep track of where my towel was, was huge. If I wanted to use three towels at the pool because it's chilly when you're going through the North Sea, I could.
Other things I preferred on DCL: no loud and smoky casino, no art auctions, no super loud music in the pool area. If I never hear another steel drum, it will still be too soon. The only thing on Carnival that I liked at all was the kids' clubs, but the DCL Oceaneer's club and lab had so much more to do and I felt like there was a much better ratio of staff to kids.
I felt like the food was fine on both. The DCL food wasn't as amazing as I'd heard, though we were still eating a ton of it. We thought we would try to get a Palo brunch, but the thought of even more food was totally unappealing, so we didn't do it.
If I wasn't physically uncomfortable in the room on the Carnival ship for the entire 7 days, maybe I would do it again for a cheaper option for an Alaska cruise, but we had engineers in the room daily working on the A/C and they could never do anything about it, and I never want to be on another one of their ships.