is an intake valve larger than an exhaust valve in a cylinder head?or is it the other way around?

Answer 1

intake valves are larger to increase volumemetricefficieny meaning the atmospheric pressure to push the fuel and air into the cylinder where a the upward movement of the piston in the exhaust stroke pushes out the burnt fuel

Answer 2

Exhaust can be smaller because the exhaust valve opens before top dead center (pre-exhausting), so you get the gases out under pressure.

Answer 3

Cold air and fuel is heavy dense. Hot exhaust gasses light. Bigger valve heavy dense air fuel. Smaller valve for hot light gasses.