Yes, they are both good in their own departments but I would rather pick Eminem because 1. he's a rap legend, rap is not just about rhyming, its about the flow and the actual meaning of the lyrics, 2. hes hott, 3. he's got a nice body, 4. he is SO not overrated, how is he overrated if people keep saying he's overrated, and no one is overrating him..if that makes any sense at all, 5. he's not going downhill, he's gotten..about 5 hits from his new album, although Usher has done himself good with "Yeah" and "Confessions" and all his other overrated songs. So yea.
But thats just MY opinion