John,

Dollar for dollar, the ML63 is a bargain against its closest rival, the Cayenne Turbo. Add the GTS and it makes the ML a better deal. Being a Mercedes man you know the quality. The ML gives up little if any to Cayenne in terms of performance, seating, space, towing, off-roadability, etc. I love my Porsche's and spent much time with a turbo (never a Turbo S but that was out of my price range) but ultimately decided on the ML and never regretted it until my lease was up. I no longer needed an SUV so I didn't replace/ keep it.

Although....I have spent some time with lesser ML's (350/ 500) and was actually unimpressed. With the ML63 you essentially get all the packages and goodies; those you have to pay extra for non-AMG. I think in every version of the Cayenne, the "base" package is quite good. If no ML63, definitely any Cayenne.

 

If you are set on the Porsche and the Panamera is out then just wait. Time is on your side as the new model Cayenne is supposed to be amazing.