The ride, comfort and refinement is miles ahead of the Sierra.
The sand performance is excellent. I went to Fraser six months ago and it didn't even come close to getting stuck, I didn't even need to lower the tyre pressures from normal (I run 25 psi)
The best modification you can do is to ditch the stock tyres within the first 15,000K as they are near the worst tyres I have driven on wet roads after that point.
The next best modification is to junk the rear shocks and replace them with some OME's or similar. This will improve the rear end control over corrugations no end, greatly increase rear wheel articulation and offroad ability and also improve the ride to boot. The stock front struts are fine.
cheers,
Brian