Petcos are all corporate owned while Petlands are franchises. Petcos are usually more uniform in their practices. With individual owners (franchisees) then they sometimes do their own thing (like sell puppies from a puppy mill, etc.)
I have purchased from almost every company and would again, provided they don't undertake bad practices. Often, I too, find then to have better prices. You do have to be careful with the condition of the livestock.