AMD cards tend to be faster for Dolphin than NVIDIA cards now because they're faster at Integers.
Ever since the merge of tev_fixes_new, Dolphin has relied on integers to fix stuff that was broken before. OpenGL is more affected by that then D3D11
Ever since the merge of tev_fixes_new, Dolphin has relied on integers to fix stuff that was broken before. OpenGL is more affected by that then D3D11