Since we just added two new puppies to our household, I've been to all of the major pet chains in the past week. While PetSmart has the best selection & customer service, Pet Supermarket is the closest to me so there's not much reason to go to Petco. I went for the first time because the website listed an outdoor play pen on sale last week that was exactly what I'd been wanting to get for our puppies. Well either the store is understaffed or the staff was more interested in spending time socializing in the room at the front of the store, because I could not find anyone to help me with the item I wanted. Eventually I found the item I needed & it was $10 more than the website was selling the exact same item for. Needless to say, I wasn't thrilled but I did go ahead and purchase the item since I had traveled in rush hour traffic to get to the store and was not in the mood to take a chance that another store might not have exactly what I was looking for.
ETA: After spending another weekend buying puppy products, I can tell you that Petco is MUCH more expensive than the other stores. Items were DOLLARS more at Petco than at Pet Supermarket or PetSmart.