I see the Vega is back in stock if you had a choice a 1080 or Vega 64 what would you get.
I ownt both because I have numerous systems, they are quite evenly matched so if it helps I can offer the following advice:
1: If you're horrified at the prospect of spending an extra £10-20 a year on electricity then get the GTX1080.
2: If you're horrified at having to open a door/window because it's too hot, 5mins earlier than you would with the GTX1080, then get the GTX1080.
3: If you own a G-sync monitor then get the GTX1080.
4: If you cannot live without PhysX in your games then get the GTX1080.
5: If you use your PC for GPU accelerated applications as well as games get the V64.
6: If you plan to keep the GPU a long time then get the V64 (as the performance increase over time will outstrip the GTX1080s as AMD drivers mature better, usually due to starting out worse).
7: If you own a FreeSync monitor get the V64.
8: If you don't own a *Sync monitor and plan to buy one during the ownership of this card get the V64.
Obviously multiple ones may apply to you so use best judgement.