I have to jump on the bandwagon here and agree that longer cruses attract an older crowd. I am assuming that you and your friends are single. If so, and you are looking for any kind of nightlife or evening activity with people of your own age (and single), then the only one of your choices that would offer that possibility would be the Carnival Legend. While I am not a huge fan, I must say on my last couple of Carnival cruises, the food was very good and the staterooms were quite comfortable. For your age range and being first time cruisers - I think Carnival and Royal Caribbean would be your best choices.