Petsmart by far. Our petco is the combination of every horror story you've heard about pet stores. Abuse in the grooming facility, animals dying all over the place, horrible care advice. They also sell less products than petsmart and ours does have the tiniest bowls for fish. Our petsmart, even though they do hire teenagers like every retail business does, seems to hire only people who like animals. Their tanks are always great. The used to have a vet that was real nice. Plus they have a clearence section that's my favorite. When you can pay 19 cents for clearence tank decorations you'll be there every week to surf the aisles. Both do adoptions, but you can hardly take that as a measure of quality.