With SC2, I liked the diversification of the factions, in a sense. Adding in the jump jets for Cybrans was a nice touch, the teleport for Aeon was a little funky, and I guess the speedboost for UEF was okay, but the Aeon and UEF mobility bonuses just seemed like "we have to give them something because the Cybrans got something."
What they did to naval combat was terrible, where UEF was the only team to get non-experimental submarines (and the Cybran experimental sub was terrrrrrrible), and the Aeon didn't even get a navy. Boiling air units down to a fighter, bomber, and gunship for UEF, and a fighter/bomber and gunship for Cybran/Aeon really made me scratch my head, because it completely takes any thought out of it.
What they did with the units was severe homogenization, compared to SC1's overload of largely useless units. They tried to boil the tier system down into a research system with more longevity, but they really failed because they lost a lot of the special abilities and ideas that went into a lot of the units in SC1.
The problem with a game like SupCom, however, is because of the scale they necessarily can't give each unit the personality it should have. They're pretty much limited to adjusting based on damage, range, fire speed, hitpoints, AOE, and mobility, and there's only so many ways that can swing within a certain balance equilibrium than if you added in armor types, damage types, unique unit special abilities (activated or passive), and if you're eschewing a tier system then your total feasible unit unlocks are drastically more limited.