Id say consider any TDI with an engine no greater than 2.0L.

You'll have the benefit of lower taxes on the smaller engine and the relatively high fuel economy associated with the 1.98l class engine (avg 5.25 l/100km). Most 2.0 petrol SUV's will get avg 9 l/100km.

Assuming that a distance of 10,000 km, the TDI would consume about 525 liters and the petrol would consume about 900. Petrol at 1.85 would total 1,665 francs and the diesel at 1.95 would cost 1,023 francs. The TDI is the more cost effective option by quite a margin.