Who cares? They are the same bid category, flown interchangeably with, and pay the same as the 148 seat A320, which is not smaller than an MD88. So the 319's are smaller than the MD88 in the same way your 757's are smaller than your 767's. Same bid position, same pay on the 75 as the 76 (300's).Well they share one defining characteristic...
They are smaller than an MD88 in the same way that a 777 is smaller than a 747.
Cuts both ways.