The 2x12 works great. Obviously it doesn't have as much low end resonance as a 4x12, but it's never lacking in volume, low end and definition. It's a great cab. And seriously, what kind of inconsiderate wanker goes to a bar or small club gig with 2 4x12's? People go to listen to you, have a good time with their friends, not get their faces blown off. This is coming from a guy who fronts a metal band. Then again I've always been more practical, but I do know that the Mesa 4x12 weighs over 100 pounds. It's the best thing ever until you encounter stairs.
Just think what do I really need. Even tour bands only go with 1 4x12, maybe 2 for large venues and arenas. The Edge still uses vox combos and fender tweeds if that gives an idea of how big your amps need to be. For the average gigging musician who has access to a PA system, 4x12's are overkill.
imho