I used to go to Petco AND PetSmart. Then I just stopped going to Petco all together. The store was just old and dirty. They've moved to a new location, farther from me, and we've been in once to get an Aussie calendar.
But mainly I shop PetSmart for food and litter (also take Zoee for grooming and Tagg for nail trims). And sometimes I go to Pet Food Express (local chain) for misc things because I get a 20% discount for volunteering at ARF.

Every PetSmart I've been in has a Banfield vet in it. Its nice because you can buy perscription food there cheaper than at your normal vet. Luckily I do not have anyone on Rx food right now.