Purchase advice – New or used cars

Hello, we currently have a Passat 3BG Variant (BJ 2004 – last version) as Trendline Family. This one still has TÜV until Nov 2017. In the near future the following is probably due: – new set of summer tires – new set of winter tires – possibly clutch – cold start problems of the vehicle can be analyzed – rust on the trunk flap of the Variant mileage are approx. 100.000km. We got last year family offspring no. 2. In place we currently just get there, in the K now we could get a new VW Touran 1.2TSI for approx. 25-26 T EUR with some equipment. The new car is really great and would suit our needs with the children well. Now we are really thinking about whether we should take the money into our hands (via financing) and buy the car or drive the Passat 3BG still until at least the end of the TÜV period, well known Do you have pros and cons, experience reports or decision reports for getting the old or buying a new car? Thank you very much!