I would say my local Petco and Petsmart are about even as far as caring for their fish. Petco seems to have a better selection of bettas and I generally prefer shopping there, but their fish care has been declining lately. My fiance and I found FOUR dead bettas on the display the last time we went in and a VT with finrot so bad that his fins were almost gone. At another Petco in the area, I saw one with a really bad case of popeye. I felt so sorry for both of them.
In both cases I wish the stores would let me take care of their bettas. I would do it for free!