When compared to the Ford the MB 2.5 CDI should well exceed your expectations (personal opinion).
They have sold Vitos with the same engine as well. Go Yahoo UK etc for info.
http://www.vankempen-autosport.nl/engine/tuningbox.htm
An interesting place for performance enhancements!
Note do look at the aux heater if you are in cold climes it will come in handy and prevent the need to idle the engine for long periods. I am hoping it can be used to prewarm the engine as well but have not checked into that yet.