Let's see... Alabama has had a vanilla offense and has only needed a serviceable QB to get the job done. AJ McCarron has been just that and wasn't that special (although let's not forget he was a heisman candidate despite being incredibly average), so he really isn't that hard to replace. Ohio State does not run a vanilla offense and needs a QB with a high football IQ who can distribute the ball to playmakers. This is more difficult to replace, and lets not understate Braxton's role in the running game.
Though on the surface, the situations between Alabama and Ohio State really aren't all that different, but it's not difficult to understand why the Ohio State QB is going to have a steeper learning curve than the Alabama QB. Alabama deserves the higher ranking because of this, and the fact that their defense is much more of a proven commodity than ours. We like to think our defense will be top 10 this year, and they probably will, but we haven't seen it demonstrated against live competition yet. Also, yeah, strength of schedule. Alabama won't be tested until the last few weeks of the season, whereas we are tested from the onset and continuously throughout the season. They have time to break their new QB in, we don't have such a luxury.