It's definitely interesting to see the results here, the good old ground tent still prevails! It's currently my preferred method as well, for several reasons. First and foremost is what my Overland vehicle is: a lifted WJ. It's pretty tall (I haven't measured, but I can tell you it doesn't clear my 7' garage door by much) so a Roof Top Tent would be way, way up in the air. Also, a RTT would mean I can't park it in the garage. Also, it's a lot of weight way up there, my Jeep is setup flexy (though it does have Antirock sways front and rear) and I like "challenging" trails so I don't think I want 120+lbs on the roof. Also, the WJ is actually pretty small and the bigger hard-shell RTTs I'd choose (no way I'm going RTT and dealing with an annoying cover and stuff) would have a big "mushroom head" look on it (yeah, it matters to me a bit). Finally, there's cost. Any of the RTTs I'd consider are $3k plus. I already spent way too much doing my build in 2020, I need to chill out on spending on the Jeep in '21. As for other options, like a trailer or sleeping IN the Jeep, well my choice of vehicle and type of Overlanding also limit those. My flexy suspension probably wouldn't be the best for towing a particularly heavy trailer. I know it can, and has been done, but personally I don't want to drag a trailer on the trails I do. Also, we have an RV and do 'camping' trips like that when I need/want all the amenities of home. The entire point of the Jeep for me is quick, simple, back-to-basics trips where I don't have to deal with the hassle of a RV or trailer. As for sleeping in it, my choice of a WJ bites me once again, in that they're just not long enough. Technically if I made a platform that would fold forward when I slide the passenger seat alllllll the way forward I'd fit, but I think it'd get to be very "coffin-like".
I like the space of a ground tent to have my gear and keep it clean/dry. Easy to change or take a "hooker bath" (baby-wipe clean-up, though now there are many wipes made for this purpose that work much better). There are downsides of course, like having to find/clear a good space for it. Less protection from critters (whether real or just "feeling" safer). And a bit more time to setup/take-down (vs. sleeping IN the Jeep or a hard-shell RTT, really no more time than a soft-shell RTT). The ground tent's biggest drawback is on trips where you move every day. Then it's sort of a lot of setup/takedown. Back on the plus-side, on multi-day trips where you establish camp but go out and adventure during the day, you can leave your ground tent setup, unlike a RTT or a sleeping setup inside the vehicle that makes it undriveable.
-TJ