Bill Connelly, the S&P+ numbers whiz, published a great piece this morning that addresses each of the four teams' chances of winning their semi-final game and winning it all: http://www.sbnation.com/college-football/2016/12/6/13853014/college-football-playoff-2016-preview-alabama-ohio-state-clemson-washington
Key takeaways: He estimates the Bucks have a 62.1% chance of beating Clemson. He then gives them a 41.2% chance of beating Alabama. Overall, that yields a 29.1% chance for the good guys.
Alabama, by contrast, has a 44.8% chance of winning it all.