Hmmmm...definitely not on Royal. Matt's got a good lock on group cruises there, and I'd love the opportunity to try a new cruise line with a bunch of friends. But I'd totally be open to Celebrity, even though we've sailed on her. No Carnival. Last time we sailed NCL it was still called Norwegian Cruise Lines, before they switched to freestyle cruising.
Probably Caribbean, as Florida ports are probably the easiest for most to get to.
Maybe one of the medium size ships, that allow lots of different group activities.
What would separate it from other cruises? Other group cruises or just other cruises in general?