Well i think they can do alot, but there are just too many things to break on those rigs, and the parts are few and EXPENSIVE. ( i looked into getting a discovery....the rig was cheep, but the parts....ouch).  When BMW owned that company....and they were shoving M series engines, and that massive v8, those were proper rigs.
Defenders are still the ultimate Land Rover.....but i still think the jeep TJ is the ultimate offroad vehicle ever. It's just soo cheep to maintain, versitile, lower gear ratio( i hate to say this, but Jeeps have much more torque then the range rover.......the 6 speed 1 gear low end is 5.014:1  and the rangerover is  4.7:1.....although the defender does have a 5.77:1 gear ratio)
They are just two different rigs, the Jeep is a spartan anything beast, that can be built up to the ULTIMATE rig.
The Range Rover is a lux offroad anything machine that has little modification potential.  In the stock form you can go tons of places with a range that the jeep can't go, but as soon as we talk mods then the TJ is the most versitle offroad vehicle in the world.