[Brainchild]

I'll be blunt and say that I don't like either of them at all.
Shinji is a gullible piece of jelly for almost all of the show, and while I can't say I'd be any different given the situation, he just seemed to be too forgiving and lacking in conviction. Added to how naive and overly trusting he was, I just found him to be irritating.
Ren, on the other hand, is just too cold. He, in complete contrast to Shinji, is nothing but conviction, and doesn't have the ability to put others before himself, like a traditional hero character should be able to. (His fiancee doesn't really count as far as I'm concerned; valuing one person's life over that of multiple others' because of a relationship is fairly selfish.) Beyond that, he just seems to be trying too hard to be cool.