I don't personally have experience with an rtt but have gone camping with my friend who uses it quite frequently, the only time I get nervous on his behalf about the center of gravity was during grade 5 4x4 obstacles, he drives a 2.7 ifs hilux so with the suspension travel the patrol has already makes it quite safer on a 4x4 track and the Patrol is very heavy. The previous owner of my previous Patrol loaded 300kg on the roof and he claimed didn't even notice the weight. I know the Patrol is actually rated at 100kg.
December my friend was in the Kruger and it rained quite a bit, if it was not for the rtt everything would have gotten wet and muddy during setup but because everything is enclosed in the rtt there was no problem, never mind all the creepy crawlies also looking for shelter. During my Namibia trip I used as ground tent and while at Sesriem quite a wind came up and I was quite upset when I found most of the dunes inside my tent, but that all depends on what tent.
If I camp for more than 2 nights on the same spot a ground tent makes much more sense since everyone else always waits for the guy with a rtt to pack up his camp just do drive his vehicle.
A rtt saves so much space because the bulkiest items I have in my vehicle is the mattes, tent, sleeping bag and all of it can stay inside the rtt.
I am quite for a rtt and would probably be my next big investment before a trip such as yours.
Hope I helped.