I cannot see how you can describe Poch as proven. Here's his managerial record....
Tottenham Hotspur
Individual
Basically, he's achieved nothing of note and never held meaningful silverware above his head. How can this possibly make him ready to lead by example one of the most successful and popular clubs in the world. Whoever manages United carries a weight of expectation from fans, the media and investors that's massively greater than the same expectations of any Spurs manager? Only Barca and Real can compare with our manager's role.
On top of this, it's pretty obvious we have a 'nice' manager now and the players get away with murder under his oversight. Do we really want another manager the players will like?
I want one they will respect for his own achievements (managerially, as opposed to on the pitch), listen to because he knows what he's talking about and also be a little bit afraid of as he's willing to take a hard line with them when needed.
Allegri would be my choice.