The thing about Eminem vs. Nas is that is goes back to that fundamental basis of what you want from your lyrics. Nas has always built intricate verses where he is telling an actual story, conveying a message, or just speaking on something real. A lot of Em's bars aren't about anything at all. So it just goes down to what you want. Do you want someone like Eminem setting up multi with the sole purpose of talking about how he raped some chick or do you want a dope verse talking about politics? I'll go with Nas every time