And that's why people validate getting Vega if you do not have a G-sync or Freesync monitor and wanting to upgrade both the GPU and monitor. The Vega 64 is inferior to the GTX 1080 it is targeted at. It costs the same*, performs lower, and uses more power (a LOT more power). However, the Vega 56 is better than the GTX 1070. But it costs more* and uses more power. The only real advantage Vega has over Nvidia's Pascal is the savings in buying a Freesync monitor over a G-sync one.
*That's referencing the announced release prices, not actual selling prices. I'm leaving out the upside down reseller price structure right now between the GPUs due cryptocurrency miner demand throwing them all out of whack.