r9 or gtx660?

I can't decide on graphics card... What card still should perform good after 3 or 4 years?

P.S. Sorry for my bad grammar!

r9 what? 270x I'm guessing? I would go with an r9 270x, it's a bit newer and http://www.hwcompare.com/15671/geforce-gtx-660-vs-radeon-r9-270x/ 

The 270x is technically faster...

If I were you, I'd get an R9 270 with an Asus direct cu ii cooler and overclock it.

Because it will support mantle and as a general rule, I try to get the newest card in my price range. 

Good luck!

R9 270 because it is a new card that comes with an aggressive price point that is hard to beat. But, nvidia has features such as shield, TXAA, PhysX, and G-Sync (We are unsure if Gsync comes to amd cards). If I were you I would just go with the 270, overclock it, and spend the extra $20 on games.