A few years ago I found myself in my Def 110 accompanied by a bloke with Disco 3 in rural Russia, Kostroma region, on a very muddy track. The Disco 3 had all bells and whistles, plus much more of aftermarket stuff, and coped with the terrain quite good. In fact, on same occasions it was better than my Def, what had just AT tyres, otherwise - bog standard.
It all lasted, until Disco started to fire under the bonnet. We quickly extinguished it, but... Some electronics was fried, and fancy air suspension was nonoperational. With Disco 3 laying flat on its belly it took us next day and a very big tractor, sourced 40 kms away, to get the bloody thing out. 2 more days to get the Disco to the nearest dealer, where it was quoted in excess of 4000 euros...to diagnose! Not to fix, but to diagnose whats wrong with it!
If that would have happened to the Defender, well, some replaced wiring later it would have happily continued.
And the lesson? No thank you, if I'd need a transport for overland, then no new Defender for me, nor any of other LandRover products. Too much to go wrong.