It depends on what you need, really. Amazon has a ton of products from every sector of the global economy. Best Buy has lots of electronics, but more for the mainstream purchaser. A store like Microcenter does have electronics, but is geared towards people that really know what they're looking for - my local one has the back third entirely dedicated to PC parts. I put mine together from there. Amazon will never be able to replace window shopping.
But many people window shop at the stores, "kick the tires" as it were, decide what they want and then go buy the product at Amazon if it's cheaper.