Oversigning is a huge advantage, and seems completely unethical to me. They're making themselves into football mills, not institutions of education, with this practice. It's a tragedy because it screws a lot of kids who could have gone on to careers at other schools.
The biggest perpetrator of the superiority of the SEC is ESPN, who (shockingly!

) has a $2 billion contract with the SEC. It's very much in the best interest of ESPN to continue to pimp the SEC. It's a shame that they purport to be a sports journalism source, yet they are very clearly a biased source of information.