I've never purchased fish online, but I will offer some thoughts. I would always prefer buying fish from a local store/importer. If they should die, most stores will give some form of credit. Online, this may be difficult or bothersome. And I like seeing the fish before I buy it. Fish often arrive in transit severely stressed and prone to ich, and I would prefer the store deals with this rather than me. Many fish arrive dead, or near death, and the store has to bear this loss but again, I would rather they do than me.
From my info on the Wet Spot, I can't imagine any online retailer bettering them.