Unless you get a trailer, your going to be cramped in any van with that many people + gear. Think extra insurance + paperwork + place to park the trailer. I would also be worried about some douche bag breaking into the trailer or flat out stealing the whole thing (along with all the gear)
The reason why I say this is because last year I took a 12 passenger van from LA to Portland, OR with 10 people + gear and it almost made me go insane. So cramped, dudes falling asleep all over one another and drooling. It was fun, but not for 20+ hours.
How far are you planing on going?
Busses are way cooler than any van in my opinion, especially if your not married. You can build out lockers into the busses walls, and floor for extra storage and security.
It would probably be cheaper to pimp out your bus with an AC, new exhaust, some couches bolted to the floor, exc than to buy a new-ish van.