So I asked this directly to Claymore however he suggested I ask here(I have edited it slightly):
I have 6 x RX570. 3 x Aorus 4GB RX570 and 3 x MSI Armour 4GB RX570.
If I use SGminer, the Aorus get between 800 and 850h/s and the MSI get under 800
If I use Claymore miner, the opposite. Any ideas why this might be?