I think much of this depends on the vehicle. When I had and Eezi-Awn RTT on my Discovery, I thought it was a ginormous hassle. It was just high enough off the ground I had to climb up on my Disco a dozen times to get it fully deployed, and another dozen times to get it stowed. Seriously, it was step up on the tire, fiddle, step down, go to the next tire, step up, fiddle, step down.... I also really disliked the added weight on my roof. Didn't feel unsafe, but it did feel weird.
I guess I don't mind the ground tent. I'm a buyer for an outdoor store, so I literally buy outdoor gear for a living. I guess I just chose my tents carefully as well as all the goodies that go in them. I also like a shelter that's useful for more than just laying down. This is why many RTT users have awnings.
I won't say that setting up a ground tent is any quicker or easier than setting up an RTT, I'll just say that in my situation the RTT was anything but "Eezi." Kind of a PITA, actually.