I love G wagons and Defenders and agree the G's are bullet proof. I have two 2014 G550's (one for me and one for wife) with AMG wheel package. Much too new and pretty to really use for serious off road right now, but I have done some off roading with it and was extremely impressed with the three locking diffs. Turn radius is not great though.
My Defender is a 1994 and although I love it and can say get used to frequent tinkering, although the one you are buying looks to be quite nice.
Good luck with it!