I have to say, completely excluding the drumming aspects of things, I want Mangini the most. I just want to hug the guy in the first video when he's talking about how much he wants this.
There's something that I want to point out though... and that's this: they showed us Mangini's interview with the band, where he restates what he did to the camera earlier: I'm not here to, in any way, replace Mike Portnoy. Mangini is set on making that as clear to us and the band as possible, and after that, Petrucci explains that they're looking for somebody who is willing to step up to the plate and be that replacement. Now, Petrucci segues his sentence into saying "And I feel very comfortable with you playing.", so it's not left on any odd disposition, but still... that stood out to me as a possible, "Maybe Mike Mangini did not get the part, because he does not want to overtake Mike's role in the band's career."