I think the 2.0 CR170 engine is one of the most reliable VW made.
This
+1
I ran a 6spd manual CR170 A3 Black
Dishun' which was revo stage 2 mapped most of it's life under me (4 years) and it was bulletproof, or certainly seemed it. I serviced it every 10k (oil/fuel filter/filters etc) but despite being well treated, it always was ready for a hard drive whether it be around town, motorway haul or on track days
Nothing on it felt anything other than on about 20k miles bearing in mind I sold it on about 92k. In honesty, it felt like it was just wearing in! A few things annoyed me about it but that was mainly Audi design and their inability to spec even the top of the range Audi's at the time properly (2011). The GTD won't give you those niggles. In terms of mechanical reliability, my CR170 was better than my MK5 GTI, of which only the AC compressor ever let me down in 3.5 years
Find a well serviced one and the mileage almost doesn't matter to some degree, either negotiate a warranty or get a reputable well priced used car warranty for peace-of-mind. Choose well & job should be a good-un. Bear in mind in this day and age, some of them could obviously already be mapped but the nature of the seller and drive of the car under test should reveal if that's the case or not