I pick Alabama primarily because I've never seen Nick Saban fail to win the title when he has a defense of this caliber. It fell way off in 2013 and 2014. The last time they won the national title the Tide allowed 2.43 yards per rush, best in the country. This season is even better at 2.30.
I think Alabama will establish Derrick Henry and methodically control the line of scrimmage.
However, I'm not betting this game. The surreal bargain was last week, with Alabama facing a joke Michigan State pass defense and a team that had no business being in the final four. Clemson is much more legitimate. In fact, the YPPA Differential actual favors Clemson at +2.3 compared to a very pedestrian +1.5 for Alabama. Last season I pointed out on this forum that Ohio State and Oregon were tied for best in the nation in that stat. They were each something like +3.4, if I remember correctly. So while Alabama may have looked overwhelming last week it was largely due to the inept opponent. Alabama can look quite beatable at times, notably against Arkansas, Tennessee and most of the Auburn game, not to mention the game they actually lost against Mississippi.
I'm rooting for Clemson even though I expect they'll fall short. The key for Clemson is to bust the big plays into the end zone and not allow Alabama to line up again. Also, Clemson needs to prevent the Alabama quarterback from slivering away and connecting on deep balls after the play has seemingly broken down. He doesn't look like an athlete but is surprisingly nifty and dangerous on those plays. Those plays altered the game against Auburn. Overall Alabama only averages 7.3 YPA, which is low for a national title team and the reason I don't consider them a shoo in.