I got a Sapphire RX580 Nitro+ Limited Edition at 27MH/s, estimated to mine 0.01X ETH per day. The whole setting consumes ~500W/h (it would be more power efficient in multi-GPU), you may take mine as reference. AMD is saying to be better than NVIDIA based on the power efficiency. You can see the higher hash rate of 1070 / 1080, but the price is higher as well.