...Just because he is white doesn't mean that they are worth comparing. Mac is so relaxed he's boring, and Eminem yells, along with many other differences.
Mac has too! He came to Ohio a few weeks ago and that sold out. But the only reason Slim has more is cause he has been in the game long than Mac has. If Slim retires right now and Mac went for as long as he did, Mac would come out on top.
There are myriads of better white rappers than Mac Miller. As I said, he puts no effort into his voice, and his lyrics are average. Some better white rappers are Asher Roth and Classified. (Both in Madden 12 I've been told.)