The GTX 1080 and the RX Vega 64 are practically the same, at stock, but the Vega 64 seems to be able to consistently push out a few additional frames more than the GTX 1080 at higher resolutions (perhaps due to memory bandwidth), although we're talking like 3-5%. Whether that is tangible in a multiboxing setup, I don't know, so it probably just comes down to your budget and whichever can be found cheaper when it's time to make the purchase.