Depreciation-wise I wouldn't buy a new C5, I would however buy a nearly new one.
Of the others the X-Trail is compact, fairly economical and is a good, reliable performer. However as 'vans get ever heavier it looks quite lightweight in comparison to some of the others. That said my father in law is changing his as he feels its too big now he is retired! Getting an Astra SRi estate instead, with which he will tow his 1200Kg Bailey.
I do like the look of the Freelander 2.
Value for money and all round competance places my vote with the Sorento though!
Alternatively your money could get a nice nearly new A4 3.0TDi Quattro - all the best folk have them!