I considered a Jeep Cherokee 2.5 diesel before settling on my Discovery.
The main thing with the diesel seemed to be that pre-1997 (I think) engines were
very prone to cracking!
There is a Jeep club forum at
http://www.jeepclub.co.uk/forumindex.cfm where I got some useful info.
I received this from a Jeep expert:
The 97 on XJ had the improved diesel which is less prone to cylinder head failure. '97 model year began with the start of the facelifted XJ with the modern dash, etc.
Hope that helps!
Cheers,
Gordon