Which V6 Cayenne - 955 or 957 ?

[Spy]

I am looking at returning to 4x4 ownership having previously owned a Range Rver Sport, Freelander and CRV.

I am looking at early-ish Cayennes with the V6 petrol.

Interested to hear opinions if a face lift (957 - 3.6) Cayenne with high miles (day 120 to 140k miles) is a better buy than a Facelift (955 - 3.2) car with lower miels (say 80k miles), assuming service history and condition are similar ?

Also, I have read that the fuel consumption of th V6 is similar to the V8, how true an how close is the mpg between these two engines ?