What did you call Ashley bitching about the aliens?
Something that actually makes sense.
All Kaiden did was whine about being pushed around by a Turian in his school when you talk to him, but otherwise his interactions outside of the Normandy with you are incredibly... Plain. Like Alex C pointed out, all he has to say about things are just general, good two shoes thing. Ashely, on the other hand, has a much stronger moral code but at the same time it's at odds with a lot of things. If she were Shepard she wouldn't be entirely Renegade or entirely Paragon - she'd be a realistic balance.
Kaiden, on the other hand, is just boring to me. He mildly complains when you do something he doesn't like - Ashley goes, "What the hell, Commander?"
As for Jacob: I like him, but he does seem like a fish out of water with Cerberus. It still kind of makes sense, though: if you ask him why he joined Cerberus despite its past, he says they've changed some and he wants to be with them because they're actually doing something, whereas he felt like he was wasting his time in the Alliance and with the Corsairs. I also like him because he's an awesome squad member (pull, squad inferno ammo and high survivability? Yes please!) and I like his theme.