As the title says. I'm deciding what graphics card to get for my new system, and i'm stuck between these two. I plan on using my computer mostly for gaming.
Not sure why exactly but a lot of gaming benchmarks suggest the R9 290 is very close in performance to the R9 290X. Also its well known that a lot of first batch R9 290s were actually R9 290X with fixed voltages. Unlocking the voltage in the BIOS basically made your 290 into a 290X! I know a couple of vendors that sell "voltage unlocked" 290s.
By "better", do you mean which one costs about half the price of the other? That would be the GTX 770. If you are looking to spend 290X money, then you would be looking at a GTX 780 or GTX 780 Ti.