Both engines are reliable if looked after from what I've read, very nice car in Titanium. Newer model Passat Highline (with full leather) and Sport models are a nice car for very decent money now. You should get an early 2.0 TDi CR engine for your budget, which are a vast improvement on the 2.0 PD.

If you go for the Mondy, I'd def go for the 2.0...the mondeo needs it - it's a big car!