Most of the mechs I (try to) compare to real life counterparts- giving room for advancements because they're mechs with super generators. 

The Bulwark is actually a pretty easy comparison for me, as I looked at it and thought to myself "That's an Abrams Tank." Which means thick armor and a big ole 120mm cannon. Though honestly, the scale on that picture is ridiculous, as the cannon's bore looks to be about the size of a man's torso.