Well Roland the answer is air. And it does make a difference. For the Marks i also prefer either traditional or stilleto cabs. I find the new rectos to be very boomy and loose. And while the hand does have a lot to do with it, stacking the cards out of your favor doesn't help. And the reason for the boominess is the size of the cab. The recto cabs are really big. Even compared to Marshall or Peavey cabs. And it affects how the cones vibrate. My vote is for the smaller cabs. Again i agree that 90% of tone is your hands but making that other 10% perfect can be the difference between a good tone and a great tone. My 2 cents.
Peace,
Joshua