We have sailed on RCI (Brilliance) but not a Voyager class ship. We have sailed on Century and plan to do so again next October. My son and his wife are about your age, and they loved Century (planning to go with us again in October). Century has a class of her own, and is one of our favorite ships. However, if you are expecting all the glitz, the huge amount of space, and the number of activities, a mall in the middle of the ship, you're probably going to be disappointed. They are two different types of cruises.
For service, Century is what I would describe as continental style, elegant, and restrained. The staff is friendly, but tend to speak to you after you have initiated the contact, rather than them coming on to you. Don't expect towel animals, they don't do that. The waiters will not be doing the organized singing and dancing routines. We got a kick out of some of that on RCI, but don't feel the "need" for it, and actually prefer the service on Century.
The food on our RCI cruise was very good, and I feel comparable to Celebrity... however we prefer the food on Century by a small margin. They will feature good quality, and the recipes will be a bit more risky, with great sauces and a bit more flair. As a a result, some people may not prefer the Celebrity menu because they "don't get it" or prefer food that is more traditional.
In the end, both are great cruises, and it's a matter of personal preference. My personal feeling is if someone doesn't like either cruise, they are probably too picky.
Don't worry about it... go with an open mind that you get to try something different, and ENJOY!
Bon Voyage!
paul