Extra power does increase the tendency to spin the wheels when in difficult situations, however, it all comes down to driver ability. I have seen a stock Susuki Vitara out perform a Discovery with lockers whilst rock climbing.
With regards to breaking something, I'am sure LR would have taken that into account when they design their vehicles.
If the driver of V8 "cheap" in Moab was a dedicated rock crawler he would have installed a hand throttle to refine his acceleration; It's quite possible that the V6 'cheap' had one fitted.
As I drive a 4.7L supercharged discovery, and off-road quite a lot, I must say that even with the extra available power (when it's required), I have very seldom experienced traction problems even with rock climbs, although I haven't done (Moab style) rock climbs.