It's interesting that 9 of the 10 teams in the rankings I posted are in the SEC.
As I posted, I don't know the methodology for computing those rankings. Nor do I know the methodology for the "Power Rankings Guru" rankings that Utee posted.
I can see two distinct different ways of computing these rankings. One would be to use power rankings. The team with the highest average power rankings of its opponents would seem to have the most difficult schedule. But "strength of schedule" doesn't necessarily mean the same thing as "difficulty of schedule."
If my team has the highest power ranking, and its 12 scheduled opponents are ranked #2 through #13 in power rankings, my team surely has the highest strength of schedule. But if my team is power-ranked #50, and its opponents are ranked #20 through #31, I'm probably going to have a harder time running the table than I would have in the first example.