I used the A-20G-25 with rockets this morning and got a ton of kills. The A-20 is fast, durable, and has lots of dakka-dakka.
Still, I've come to the conclusion that assault mode is a waste of time. The bots win every time. It's just one monotonous wave of enemies after another. The rewards are so low that you're surely better off playing regular arcade instead. It also seems to encourage the mindless furballing that is already rampant in arcade.
So I'm saying "no thanks." But for those who like it, try the A-20.