I think it is a little complicated for a categorical response.
Semiconductors do not like to be switched on and off. Neither do they like to run really hot, and some heat sink compounds can dry out.
Electrolytic caps (aka power supply caps) do not like to be turned off and on. But they really hate being hot.
All told, I think that turning on and off is better for a unit that runs hot. Especially if heat is inconvenient, or you don't own the power company.