I think Leftwich will be better then 'em all. For the record, he runs less than all those guys, but regardless, he's a good pocket QB and possesses a cannon for an arm. Brooks just doesn't seem to be able to put it together for long stretches, but Leftwich is young and has a thirst for winning, and the work ethic to match. Young could be like Michael Vick simply because of his insane athletic ability. If he improves his mechanics, he could be better. He's a freak athletically. He might be more suited to play WR, but you know QBs are stubborn when it comes to switching positions, especially ones that will go top 3 in the draft. This isn't Antwan Randle-El we're talkin about here.
In the end, Leftwich will be the best.