In some ways, I think that you may have just answered your own initial questiion. If you have gone on one cruise line and enjoyed the product enough to consider future cruises on that line, then the likelihood is that you will be satisfied on a world cruise as well (however, keep in mind some of the differences between longer and shorter cruises). As I noted earlier, please don't even consider a world cruise on a line on which you have never travelled - while other people may have loved the line and while others may have been disappointed, until you have experienced it for yourself you can never be certain that the line (or the individual ship) is right for you for such a long trip.
I would certainly be happy to try to respond to other questions or concerns. I do very much envy that you are able to consider a full world cruise.