This was the first time I (or my mom) had cruised with anyone other than Carnival, and we'd been told to expect that Celebrity was far superior. Interesting that we thought they were about the same, which is not that bad as we've been pretty happy with Carnival.
The ship was 90,000 GRT which made it easier to get around than a much larger ship like the Victory or Conquest. We were never that far from stairs or an elevator. We were midships on the third deck which was very convenient to the guest relations desk. It was also very quiet despite being right below the casino.
There was a fair amount less drinking and loudness than on a Carnival cruise, but I did find that Carnival cruisers were friendlier. Most everyone we met on the Summit was very friendly, but we overheard conversations that let us know there was some "better than you" attitude here and there. Actually, the Summit cruise was about two hundred dollars cheaper than a very similar cruise on the Carnival Victory last year -- the one difference being one more port of call on the Victory. Thus, Celebrity was a bargain, and there were some points where Celebrity did outclass Carnival. I don't remember Carnival providing a pitcher of water and a bucket of ice in the staterooms. The Celebrity cruise director (Damian) did not jump up and down about tipping and giving the ship a perfect score on the comment card. There are educational lectures about the islands and while there are a number of art talks basically centered on getting you to buy something from Park West Galleries, there are activities involving flower arranging or scrapbooking that didn't seem to have any monetary angle -- something that's hard to find on Carnival.
Mostly, Carnival and Celebrity were indistinguishable. The menus were very similar -- chilled soups throughout the week, lobster and baked Alaska on the last formal night, soda packages, and so forth. The professionalism and friendliness of the waiters and cabin stewards were superb on both lines. I suppose if a system works, there's no reason not to emulate it.
There were a few glitches. The ship had a problem with norovirus the previous week, so we were not allowed to get our own beverages and such for the first few days. (The norovirus issue also caused a long delay in embarkation.) What makes me a bit unhappy is that the same ship had a problem with the norovirus two months ago and that very week, a different Celebrity ship (the Mercury) had also experienced an outbreak. Maybe it's bad luck, but it seemed like the line is doing something wrong.
Also, the crew did not take the muster drill seriously at all. We didn't run into any first time cruisers, so maybe they figured it was unnecessary, but the crew members giggled and chatted. It was impossible to hear anything about emergency procedures because of all the jocularity.
The dining room was very loud, and made a bit louder with live classical music. (Actually the music in the atrium and the dining room was much, much less obtrusive than some of the blaring bands they have on Carnival, but in the dining room, it was still too much.) The wake-up call system is primitive compared to Carnival's. So, all in all, it was equal. Except for the apparent problems with norovirus, I suppose I'd be a bit more inclined to go with Celebrity in the future than Carnival if the prices were the same, only because there was less rowdy drinking and more activities geared towards enrichment.