Shimano: There’s absolutely no difference in brake fade. The benefit to hydraulics is better modulation, there’s a more linear progression of braking power. Plus, the hose won’t get contaminated like cables and housing.
Magura: Mechanical disc brakes will not suffer from boiling oil, but from melting of other components, spongy feeling and bad modulation from mechanical cable and housing. If mechanical disc brakes would be top, then MTBs and cars still would use them!