To be honest I’ve been running like this:
AMD = best bang for buck
NVidia = best bang per Watt.
AMD drivers are no longer their weakness - meanwhile there does seem to be some NVidia issues.
DX12 is the Achilles Heel of NVidia, but it isn’t a killer because even though it separates the RX480 from the GTX 1060, the GTX 1070 & 1080 still kill anything AMD can currently put up against them. IF the RX490 produces GTX1080 levels of performance under DX12 for the price of a 1070, then they have a winner.