"I guess it comes down to reliability and price. Is the Porsche more rock solid than the BMW and is the edge in handling and braking worth the extra 5k-7k {depending on the Coupe or Roadster}."
As someone who deals in both BMW and Porsche, I would not call either marque "rock solid" if you are talking reliability. You would have to hand that title to Toyota or Honda for sure.
Having said that, both the M and the Box will hold up very nicely IF TAKEN CARE OF! If you intend to race on or off track weekly, expect to have a repair budget similar to racing teams.
