Basic comparison:
Both aircraft are simple to maintain, but I'd give the edge to the F-5, especially those with later life mods. As far as timed maintenance and component changes, I think the F-5 has the edge from what I remember. Operationally it will depend on who spots who first, if GCI is used to vector the MiGs and if the fight goes close in VR. I've been in the cockpit of both and I would rather be in the cockpit of an F-5 in a close in knife fight hands down. If I needed the speed, or course the MiG-21.
Range, F-5. Bomb load, F-5. Rate of climb, MiG-21. We also have to consider avionics and lastly (drumroll) pilot training.