The access to spareparts and the time it takes get them would be one of the benefits of the higher volumes by Porsche. Would be more of an issue with rare birds.
As far as SUV`s (or Panamera) goes, a lot of those are hybrids, and doubling up adds complexitivity + loads of weight, harder accellerations and braking and what not. Somehow lead to believe that if the hybrids were kept statistically separate, the picture would be somewhat different. To compensate for the added weigth, manufacturers tend to shave a bit elsewhere which might be less than optimal for wear and tear....
Hybrid SUV`s would require additional caution in the 2nd hand market...