cayenne turbo s? Tell which one gives good mileage,is luxurious and overall is also good.i m having a family of 4 members

This is really a matter of opinion as each are very different to drive.
it also depends on what your looking for because if your looking for a fast 4x4 its probably the porsche or the merc. however if you are looking for an off roading 4x4 then i would have to say the audi.
comfort would be the merc or the BMW. (x5)

again it all depends on what you want the car for.

my personal prefernce however would be the BMW x5 as i think this is by far the best looking of all the cars you have listed