We had a Cayenne and a Q7, both sub 60k miles very similar to drive although the 4.2tdi Q7 was much quicker than the non-turbo Cayenne and felt a more solid car, very wide and a nightmare in car parks if you actually want to be able to open the door to get out of the car.
The Cayenne surprisingly can't really accommodate much more in the boot than your average hatchback due to the slope of the tailgate, whilst the Q7 has a pretty huge boot.
We had no problems with the Q7 whatsoever whilst the Cayenne had ABS failure, electric tailgate strut failure and air suspension failure, ABS unit was nearly £2.5k to replace, rear tailgate struts £400 and air suspension release valves were £1800, so if looking at higher mileage lower priced cars just be aware that they can be painfully expensive to repair if something gives up on you.
Whilst my 996 cost me nothing but servicing costs and tyres in 3 years of ownership