Good:
-More CO choices, as mentioned (AW1)
-Campaigns have balanced difficulty (AWDS)
-Super CO Powers (AW1)
-Some sci-fi stuff to fight against (AW1; and yes, I did just say that--it's a problem in AWDS because it overtook the main gameplay)
Bad:
-Neotank and its bad relative balance (AW1)
-Kanbei being top tier overpowered (AW1; this is still somewhat the case in AWDS)
-Defense changes being non-cumulative, causing part of Kanbei's overpoweredness (AW1)
-The start of the Strength Without Weakness junk (AW1)