Of the ones I've done to completion, Doc is BY FAR my favorite. But I loathe Corso (I'm about halfway through that romance now), so if you liked Corso, our tastes in men are probably wildly different.
Vector made me regret rolling a male IA, though, for what it's worth. Even just as friends, I really, really liked him. But then my IA would talk and I'd be glad I made a male IA, because rawr. I could listen to myself talk all day!
Lt. Iresso is a nice, nice man, but he comes way too late for the romance to really have a chance at being satisfying, PLUS the female consular just ... does not sound particularly into him, which results in them not having any chemistry. I wound up rejecting his proposal just because I thought the dude could do better than my cold fish sage.