It depends, I think. I've owned a PJB rig that was a Suitcase combo plus an extension cab (350 claimed watts, 8 x 5" drivers). Though it was advertised as the best thing since sliced bread and "very loud" in their product demo video, it wasn't. It sounded great and "felt" great to play (tight, immediate response to my playing), but whether I was playing with a 4-piece rock band or an 8-piece funk band, I almost always had to dime the master volume to hear myself on stage. Even then it fell a bit short.
There are probably cabs with small drivers in the boutique category that truly deliver, but personally I'd try to rent/borrow and play through it at rehearsal before buying anything.
I'm sold on 12" "super cabs" now. I bought a 1x12" from AudioKinesis and it's probably all I'll ever need. Weighs 30 lbs, sounds like a dream and almost puts me in 4x10" territory in terms of loudness.