Best Answer is misleading by far, and the above two comments are correct or at least close enough.
1) GTX690 is similar to 2xGTX670's in performance (2x GTX680 GPU's but lower frequency)
2) 2GB per GPU, so for SLI (specifically Alternate Frame Rendering) that's only 2GB usable by the game
3) similar to a GTX1070?
Not even frikking close.
https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1070/24.html
The GTX1070 is about 3X as powerful as a single GTX670 or GTX950. If a game gave you 50% scaling with a GTX690 vs a GTX670 (i.e. 60FPS vs 40FPS) that would still only be HALF of what a GTX1070 can do.
*So please don't pull statistics out of your ASS!!
4) SLI (AFR) also can cause issues like stuttering, or no scaling at all.
Summary:
In gaming the GTX690 without SLI-AFR support is similar to a GTX950, and at best probably not much better than a GTX970 and that's assuming the 2GB framebuffer is not exceeded causing stutters.