Firstly I would not buy a car with the VAG 1.6TDI engine because I receive complaints about that engine almost daily. But if you do buy it, get it on 16-inch wheels with a decent amount of rubber between the rims and the road and less likelihood of rim damage, tyre damage, discomfort, back problems and having to fork out twice as much for 18-inch tyres as for 16-inch tyres which can last twice as long.