How fast is the RX 580 compared with the GTX 1070 with Cycles and Radeon ProRender?

The title pretty much says it all. Both cards draw about the same ammount of energy and have the same ammount of VRAM.

Before I forget about it, another question just arouse. Can I mix both cards and render with Cycles and ProRender successfully? I mean in both, the same PC or multiple PCs in a network.