Batgirl's infinitely more recognizable than Power Girl -- she's the better "mainstream" pick. Really, Power Girl's not as popular or important as the Internet makes her out to be. It's also much easier to come up with an original moveset for Batgirl than it is for Power Girl.
I don't think Batgirl or Power Girl should be in the game, but if I was running a business I would definitely go with the former.
Yeah, sadly these make too much sense from a marketing perspective, just not from a DC fan one.
The amount of trolling he's been doing to MMH fans is unfortunate. This set would be a real punch in the gut if there's not a second batch.