For me, petsmart is over 30 miles away, petco is about 15. My local petco is the absolute WORST in not only fish selection and care but in customer service. For example, I wanted a snail, and IVORY snail because I have dark blue sand. The dog trainer guy gives me a big black snail. I said, no, i want the ivory one. He told me they are all the same and will not scoop out the ivory one because he said they are all boring. I was like, that is NOT the point. I got pissed off and took the black mystery snail and walked away. Everytime I take my eskie into petco and he is there, he fawns over him because he also has an american eskimo dog. However, due to the bad experience I had inthe past with him and the snail - I just ignore him. And their bettas are more expensive.
Petsmart has a huge selection of fish and their employees are alot nicer, plus their awuatic plants are actually..ya know...alive as opposed to petco's who are dead and rotting in the water. Not sure they get any better care but everytime I am there I see someone comming out of a room with a betta in a cup. I'm guessing water changes?
As for prices and supplies - Not sure. Petsmart seems to have more tank styles but I don;t know if they are more $$ then at petco. Dog food prices are about the same