Take this with of grain salt but...
Each profile has it's "class". Infantry, specop,mechanized,armor,static weapon,plane etc. Each profile is given a "battlerating" based on it's class. There is some randomization to it, but only just enough to keep it interesting and dynamic. If a profile lives through a virtualized fight, the damage it took is stored and wll be spread out among the units/vehicles when it spawns or taken account in it's next virtual fight.
Basically, an armor group has a high probability of stomping several straight infantry groups, but it also might get destroyed due to damage taken over several fights, or some randomization (to simulate stuff like AT).
Once again, this is more like an educated guess with background knowledge, maybe Tup, Arjay, or HH have more information.