My friend and I dive out of a 14' inflatable. We have had four divers in it and if packed right it works great. Very stable, easy to climb in and out of. (as mentioned in another thread, we hang lanyards with ss clips over the side before we splash, and when you get back to the boat just clip your gear off before climbing in.)
I worked on a project last year where we had a 24' RHIB with twin 90's on the back. 6-8 divers with 5 tanks each no problem, and the same stability and ease of ingress/egress. And the thing would scoot, too!