It's all about what I want to do with the machine. I want to play games on it and the MacBook Pro is more about having a very fast computer while having lots of battery time and more portability.
I looked into it and they only had a C2D, a 9600M GT, and 1440x900 screen. Mine will be i7, 280M GTX, and 1920x1080.
When configured, the MacBook Pro with the 3.06 GHZ C2D, and 500GB 7200RPM will end up costing about $600 more than mine, with way less graphics ability, less processor speed and less resolution.
All of this to give the MacBook Pro way more battery time and better portability. I never use a laptop more than a hour or two away from an outlet, so battery time and portability isn't such a priority. If that were not the case then the MacBook Pro would be better choice for me and I'd get it. As it is, the Sager NP8690 is right for me.