More or less why I favor Nvidia's approach. Sometimes AMD pushes a capability that no one but a few test benches or games implement, not so say that other fields don't take advantage though. Not everything developed is specifically for games.
It does make a difference though. As I recall there were many titles where the R9-290 was unable to beat the GTX970, but many of those have switched around due to improvements in the games and drivers. Sometimes building a feature into a card before the software is ready is a good thing, but on the average I would say it isn't worth it.
I think Nvidia just uses their greater resources to front load as much as possible. I don't think I've ever seen more than a few percent performance increase after the initial release of a game/GPU with Nvidia. They pretty much take care of it and you get what you pay for. Though I would appreciate a little price deflation at this point, but I guess as long as we keep paying, they'll keep the prices high.