My rigs have only XFX cards, had bought from others vendors, but sold all others cards after few days.
My rigs:
XFX RX 580 8GB Samsung = 31 mh/s 95W
XFX RX 580 4GB Hynix = 30 mh/s 90W
XFX RX 570 4GB Elpida = 30 mh/s 95W
XFX RX 470 4GB Hynix = 30 mh/s 95W
Saphire it's good too, so go with XFX or Saphire.
I think you really need a power meter not just reading GPUz data
This is from the wall, not GPU-Z.