To rephrase what I said earlier, Supergirl was a proven failed property while Power Girl still had potential to be salvage given the distinctiveness of the copy and he relative newness.
This is totally true.
However, while I as a reader can
understand the rationale behind decisions made at the business end, ultimately my priorities as a reader are very different from those of a businessperson. The priorities of a businessperson are to sell comics. The priorities of a comic book reader like me are different: I want to read good comics.
Business decisions are made with considerations apart from the aesthetic or entertainment value, which are the only two things that are important for me. A comic's sales numbers do not determine quality for anybody except the accountants.
Thus, I have no desire to defend a creative decision on business grounds. The fact that Power Girl is a more marketable character than Supergirl does not change the fact she is less interesting than Supergirl was.
Geoff Johns, the character doctor, has his hands on Power Girl now in JSA Classified. While I think Johns is overrated, he does have a tendency to make characters fresh and workable. Hey, he fixed the Hawkmess which was no small feat.
I will say one thing about Geoff Johns's take on Power Girl: he had her form a relationship with other female heroes, friendships with Stargirl and the Huntress, and a mother/daughter dynamic with the original Red Tornado. The fact he was able to make her connect with other characters shows he thinks of her more three-dimensionally; Virginia Woolf once said that the surest test to know if female characters are real or window dressing for male characters is if they form friendships with one another. In other words, Geoff Johns' Power Girl adds instead of detracts. Maybe he sees something there no one else does (and certainly I don't).