You will have to confirm with Xtrail owners but the feedback i have been getting is that the 2.0L and 2.5L are not too far apart when it comes to fuel consumption (unless in really heavy traffic).
If i were to use the 2003/2004 Camry 2.0 and 2.4L as a basis of comparison, the FC on those two variants were pretty much similar (at 6km/L++ in the city) and the 2.0L owners wished for the added power of the 2.4 on highway driving and when they load up the car. The Ford Escape 2.3 and 2.0 are also another sample of the bigger displacement unit having better FC.
There was a time when i wanted the 250X then i would have added nice lightweight 18 inch rims (the 350Z rims look great on it too) and a good set of aftermarket shocks... coupled with all wheel drive and good power it should be a good drive.
