2011 is the last model year for this style ML so I vote for the Cayenne since this is the first model year for this style, and also it looks more trendy and young.
If you get the Cayenne at least you will be driving the most recent style for the next 6 or 7 years. I don't know how you feel about driving the most recent models of cars, but for me it's quite important since I consider a car to be like an accessory.