It seems heavy armor combatants doesnt get more protection (give or take the odd point) than lightly armored combatants (which I like btw, because the opposite would strongly suggest that the lightly armored combatant archetype would be non-viable), but that they do get the opportunity to hit that much harder (& more often), unless you go the archery route (getting to use all that Dex) or the Thief route (getting powers where you can attack and damage using Dex).