I say this based on what I see and what I hear JK say about CJ. I think sometimes he struggles with doubting how good he is and than sometimes it seems as though he is trying to over compensate.
The thing about Elliot is he seems to KNOW he's the man, where as CJ sometimes doubts it. Both have amazing ceilings, it's just about whether they can tap into it.
(On a side note..... What a f**king animal Elliot is. To be obsessed with recovering the way he has and get back in 4 months..... He really does seem to have it all, but as good as his skills are, his mind seems to be just as on par, if not better. Kids a killer)