If your product is bad you an always RMA it or send it back to the company, then again you can still get a doa item in a store so I don't see the difference.
Newegg= good prices and EGGSELLENG Customer service
frys= great deals and really fast shipping
clubbit= good(dont know much about them)
zipzoomfly= good for cases since free shipping, but customer service is horrible.
microcenter= a lot of instore deals, and a great retail store compared to best buy/circuit city.