This hardly matters these days. Due to growing conditions (warmer summers and wetter winters) there are less and less lower density clefts which come through.
The key point being missed in this conversation is the moisture in the cleft. A cleft which is over dried to reduce weight (NOT DENSITY) will feel lighter when made into a bat however will be more brittle than had it not been over dried. The same goes to a low density cleft, because this is less fibrous the structural quality of the willow suffers and therefore the longevity.
Forget size of bat, think of pressing to give ultimate performance !