I've owned 3 Mesa 4x12's, two slants and one straight, all V30, and I've also owned a Mesa 2x12, however, loaded with Greenbacks. (And a couple Orange 4x12's...and a Marshall 1960...)
The 2x12 was tighter in the bottom, even with the Greenbacks. The fucking thing still weighs 70lbs, and is massive for a 2x12. You won't really be missing the punch with it.
Over at Signals Audio we created some IR's with a Mesa 4x12 and 2x12, if you want to have a go with them, PM me.
All anecdotal and not a true comparison, but I really really really liked the 2x12 loaded with Greenbacks. Wish I hadn't sold it.