Lots of good d-linemen in college this year. Suh might not be the best d-lineman in the Big 12 let alone the country. I've heard a lot of good things about the OU d-lineman (McCoy I think)
If last year was the year of the quarterback and spread offense, this year is the year of the d-lineman and punishing defenses.
Gerald McCoy has been unblockable this year, but Suh is bigger and a better athlete, plus he's made more outstanding plays (blocking kicks, interceptions, running guys down, etc.). Both are first round talents, but Suh is a little better.