Depending on your monitor setup; if running a single (non-4K, non-3D) monitor either card will probably give you a stable 100+ fps, and IMO the Asus' extra 2GB of VRAM will do nothing, so the R7 with higher clock and faster DDR3 would be preferable in theory.
If you plan to run triple HD monitors, or a single 3D or 4K monitor, I would not recommend either card. Pick something more powerful. On paper your CPU (assuming you have a decent mainboard) is capable of keeping up with much faster cards.