I'll give my opinion on the two players, obviously some will disagree but that's what this place is for.
You say manziel is a runner first but in my opinion his arm is on par with EJ and his accuracy is better. Manziel is a much more natural thrower in my opinion. If he is a runner first but still throws it better than Manuel, what does that say about EJ?
Manziel is the more instinctive runner and has better quickness and speed.
EJ is obviously bigger.
Personally I think the attitude/maturity thing is overrated. This town could use a kid with some confidence.