SF Alpha 2 vs SF Zero 2 Alpha Differences


So i know there are differences between SFZ2 < SFA2 < SFZ2A
Stuff like ex characters and alpha counters/custom combos costing more gauge.
But besides those changes what are if any big game changes between Alpha 2 and Zero 2 Alpha? I ask because i notice the SFZ2A rooms are always empty and the SFA2 room has a dozen or so ppl usually playing in it. I remember the alpha counter was kinda OP in alpha 2. Guess ppl liked that better or am i missing something?