I'm not sure if they are great, but with the exception of Clemson and FSU recruiting superior athletes, and Georgia Tech running a superior system (though they are down this year), I'd say the defenses are definitely better. To me, some of this springs from geography trying to keep up with the SEC who still mostly play football the "0ld fashioned way." Jeez, look at Miami trying to slog it out when they are geographically located with the best high school athletes in the Country. Imagine them implementing what Oregon does.
The Big 12, is the opposite. The offenses are way ahead of the defenses due to Texas pumping out players that grow up in wildly efficient and prolific systems. The ability to defend really suffers (is there a plus defense anywhere in that league).