Alpina vs M … the battle of the performance super sedans

Many people ask… M versus Alpina.  BMW is releasing cars that seem to directly compete with each other.  Which would you rather have, an Alpina B6 versus a BMW M6?  Should you use BMW’s in-house performance division?  Or should you rely on an outside performance automaker to get your thrills in your four door super sedan?

The guys at MotorTrend paint a great picture explaining the difference between the two.