290x:Can be cheaper,Mantle,True audio, eyefinity
970:Less power, less heat, Physx, Game stream,G-sync, the new mfaa, and downsampling

If you have an adequate cooling solution and want the chance to save a little money when r9 290x go on sale you can get pretty good prices. Right now though i don't think there are any good 290x deals so i would probably go with a gtx 970. Any kind of 970 will be great, I went with the Windforce by Gigabyte, because when i had EVGA cards they had horrible coil whine, but that's mostly luck of the draw. They sounded like banshees screaming lol.My Windforce cards are silent, but their fans can get quite loud if you set them to go really high.
Either way you go in the end though, I think you will be happy, because both cards are very good choices. Sorry i cant say more about 290x i never owned one. The only amd card i ever had was a r7 something i cant remember which one though.

you can compare the two graphics cards right here [ Register or Signin to view external links. ] its a really tough one, the R9 beats it at some games but GTX also beats it at other games, its mostly about your brand you like the most.the only difference at FPS is atleast 1-10 frames.

Get the 290x only if its at least quite a bit cheaper and I find the 970 is a really good card, got mine today and I'm loving it managed to get 1600hmz on the core and 8000mhz memory clock.