gti as you don't do enough miles for the tdi 
Never understand this arguement

You don't need to be doing x amount if miles to see a saving. In my first year of owning the Audi i only did 10k yet saved money on fuel
5k will get you an OK car. Both have their faults especially as the miles pile on so you're going to need to factor in costs for replacing / maintaining items
As always buy on condition and also test drive several examples as performance can vary between one car and another
