Strategy/Tips? And Overruns

[Falstaffe1965]

Stuck on the seventh scenario--the one where you're trying to stop pairs of Ogres from marching down the map. So far, about the only strategy that's halfway worked is Superheavy Tanks + a handful of GEV's with singleton Infantry. Go after the Ogre's weapons first, then treads. That works for the first half of the scenario, then it falls apart.

On Overruns--I haven't used them because they seem to only result in my units getting chewed up. Is there a good strategy for using Overruns effectively?

Infantry vs. Marines--what's the difference? From what I'm seeing, their unit values are the same.