Agree with most of the posters here, on all points. Much depends not he ship you're on, also. We've been on 25+ RCCL and about 10 Celebrity. Last one was the Apex. One major difference, the one that affects us the most, is activity. We are early 70's, but find that the demographic for the Celebrity ships is markedly older, at least in activity level. Using Apex as my example - the ship is absolutely knock down gorgeous. Luxury oozes from every pore. We were on a two week B2B, and by the middle of the second week, we got bored. There were only so many aerialists we could watch, and trivia games we could play. They're big on sit-down activities. We participated in every activity that involved movement, like Zumba, exercise classes, scavenger hunt (which we loved) but there were very few of them - at least not enough for us. Going to the gym is something I can do at home, so that's not much a draw. They did have an assortment of activities at times - all scheduled for exactly the same time of day, so unless you could instantly clone yourself, you could only do one.
So if you like a lot of (active) things to do, this might affect you. I haven't sailed many of the older Celebrity ships lately, but am specifically referring to the Edge class at this point, if you're sedentary, it's perfect. If more active, you may be disappointed. Of course, this is MHO only, and confined to the few ships we were on. YMMV