Any bigger and you just lock the wheel.
As Mildred says, if you lock the wheel, you are doing something wrong.
I run 200/203/205?mm Hope M4’s front and rear and they are, by far, the best brakes I’ve used. Changed one set of pads up front (to Reds after 4 months) in nearly 3 years, riding in Alps, Fort Bill, Inners, Wales. Original pads rear. And I drag the brakes like a complete wuss. :roll:
That said, I used to have (g)Hayes with 8in rotors and they were the worst brakes ever. Ate pads on a monthly basis and still didn’t work.