We just got off our first
Disney cruise. We've previously done 4 with Princess. I spent much of the cruise comparing DCL to Princess, and my husband and I have talked about it quite a bit.
Bottom line, in our opinion, the ONLY reason to sail Disney over other lines is for the kids and the kids programming. Disney blows it out of the park for kids.
However, Princess was either better or equal to DCL on just about everything else.
Food: Princess won hands down (food on DCL was mostly pretty average, and sometimes actually rather bad), although the Tiana's Place and Animator's Palace dining rooms on DCL were better aesthetically than Princess (Triton's seemed equal to Princess)
Service: We've always left our Princess cruises feeling like we were pampered and doted over... on DCL we felt it varied from on par with Princess, to definitely beneath Princess. We didn't experience any service that was better than anything we've experienced on Princess.
Shows: The Frozen show was spectacular... but all of the other DCL shows were either on par or not quite as good as the shows on Princess. Other acts (like the magician, variety show, etc.) were equal to Princess.
Activities: DCL wins if you're a kid. If you're an adult, we felt like Princess had more.
We did like that DCL had slightly bigger staterooms, and we did enjoy the dual bathrooms. We don't drink soda, but it was nice that it was included. And we thought it was a nice touch that we got special little giveaways like the pirate bandanas, Frozen light up necklaces or the chocolate bar from Anna's scavenger hunt. The fireworks off the ship were awesome too (though the deck party was just okay).
But Princess has several things we love that Disney did not... and we didn't feel like any of the things above justified paying significantly more for Disney over another cruise line (the same itinerary on Princess with one extra day would have cost us half of what we paid for our Disney cruise). The only reason we'd do it again (if we found the right price) is because of the experience for our daughter. But we'll wait until she's a few years older. Our next cruise otherwise will be on Princess.