I have a supercharged 4.8 that runs at a peak 0.5bar. The results are fantastic and you can look on the thread on that subject Thread on RGM supercharger
The main advantage of the supercharger is the linear throttle response and low down torque gains. I just towed a heavy caravan for 2000km and completed a 4 day trip through the Kaokoland and the whole set up did not miss a beat the whole trip. The advantage on the RGM system is that it is local, reliable and works very well.
Infact after the recent trip I do believe I have the perfect 4x4
... as long as you can fit in enough petrol