They give megas 100 extra stats so there is no way all of it will go to just its attack and speed.
I give Gallade that it has better movepool and could setup swords dance but Medicham has the immediate unreal offense pressure so Gallade will still probably be outclassed.
Until it starts throwing around +2 Knock Offs easily obliterating Medicham's few "counters". It will hit with a fair amount less force than Medicham but with far more bulk and a way better movepool.





