God bless frame pacing. 
Source
http://hardocp.com/article/2014/07/23/gtx_780_oc_6gb_vs_r9_290x_4gb_overclocked_at_4k/1

In all of our gaming we have shown you today, in every single game AMD CrossFire feels smoother to us than NVIDIA SLI. That's right, the tables have turned on this issue. In fact we experienced many situations where there was choppiness or stuttering with the two ASUS STRIX cards in SLI. It was noticeable, and when we switched to AMD R9 290X CrossFire; CrossFire just felt smoother.
However, we have also found these NVIDIA GPUs aren't the best, or most valuable in this price range. For $60 less per card ($80 less with rebates shown by Amazon today) at $539 or $519.99 after MIR each or a total of $1,079.98 / $1039.99 after MIR can buy you two ASUS Radeon R9 290X DirectCU II video cards in CrossFire. For less money you'll get better performance, however you will not be able to overclock these video cards as much as the ASUS STRIX GTX 780 OC 6GB can overclock in terms of pure GPU and memory clocks. However, the better gameplay experience, performance, and lower overall price will certainly make you feel better about your purchase of the AMD cards.
When it comes to 4K gaming, we can definitively state that two custom cooled AMD Radeon R9 290X GPU based video cards are going to give you the better 4K experience, even though these have 4GB of VRAM compared to the ASUS STRIX 6GB.
Source
http://hardocp.com/article/2014/07/23/gtx_780_oc_6gb_vs_r9_290x_4gb_overclocked_at_4k/1



