I don't know Ares, but I have both the others awakened. I'd say Azazel goes from being poor to great with awakening, while Cthulhu starts out pretty damn good. I honestly can't say which awakened is better - Cthulhu's def down alone means she'll likely always be in my team, and with the added team-wide burst bonus (not guaranteed proc unfortunately) she's pretty much my star water-team player. But in terms of which will give the biggest boost? Azazel, definitely.