Oh goodness, I'd have to dig out the books. Probably.
What I remember (particularly pertinent to the thread topic) is that Heroes and Superheroes were bad to the bone. They had the best resistances to things like dragon fear, could inspire fear in enemy troops, rally their own side, sense hidden foes, cut swaths through normal enemy troops, and survive all but the most well-coordinated assaults (or regular ones if you were ridiculously reckless with them).
I believe they were point-valued at 20/50 and magic users were 50-100 (so, in effect, the game only included fighters levels 4 and 8 and MUs 8-16, so no they weren't usually going to be equal in value). However, where their point costs intersected, I honestly thing the fighter was a better pick. It would be situational, but, say, 50 points of regular infantry and a 50 point magic user or 50 points of infantry and a superhero unit was a tough choice that I think I'd rather have the superhero. The superhero-supported squad was easier to leverage, since the rest of the squad didn't spend most of its' time just setting up defensive position to protect to fragile artillery piece Magic User.