No performance numbers, just living with 980 SLi.
http://www.hardocp.com/article/2014/10/30/4_weeks_nvidia_geforce_gtx_980_sli/1#.VFToJvmsW7s
The Bottom Line
Have I been happy with my Radeon R9 290X CrossFire system? Absolutely. A new NVIDIA GeForce GTX 980 SLI setup will easily remind you what you would like changed about it however. The GTX 980 cards are so much cooler, and so much quieter than the 290X cards, it will astound you that these cards perform so incredibly well. The efficiency that NVIDIA has accomplished with this new Maxwell GPU is praiseworthy.
From a pure gaming performance standpoint, I am not upgrading in my move to 980 SLI from 290X CrossFire. From a comfort and usability perspective, the 980 SLI is twice the product 290X CrossFire is, or maybe a better way to say it would be that 980 SLI is half the product that 290X CrossFire is...half the heat and half the noise. Sadly that thinking does not extend to the half the price.
Today you can purchase a custom cooled Radeon R9 290X card for as little as $320 after MIR. The least expensive GeForce GTX 980 card for sale today is $549. If you are taking SLI into consideration that is a fairly big price bump for better efficiency. You can argue electric costs over time, but the simple fact is that it would take a hell of a long time to recoup $460 no matter how many hours a day you gamed.
Even though I am specifically talking about my multi-GPU experience, single card GTX 980 performance cannot be ignored. When you use the NVIDIA GeForce GTX 980 in a single card configuration on a sub-4K single display, the GTX 980 not only is more efficient, it is simply a better performer, and by a good margin. Overclocking your GTX 980 will push the performance even further out from the R9 290X in performance.
For 290X CrossFire users, it is very hard to make the case that it is worth it to jump to a GTX 980 SLI setup. I am not writing this to try to sell you on one or the other. Even if you could sell your used 290X cards for $500, another $600 for a set of GTX 980 cards in order to get better efficiency, less heat, and less noise is a fairly steep cost.
If you are considering a new multi-GPU system, the pricing on the current crop of R9 290X cards makes CrossFire a lot more palatable wallet-wise than GTX 980 SLI. For a long term multi-GPU purchase, there is no doubt in my mind that you would easily be happier living with GTX 980 SLI day to day.
http://www.hardocp.com/article/2014/10/30/4_weeks_nvidia_geforce_gtx_980_sli/1#.VFToJvmsW7s