Yes I have set in, driven and in some cases owned some of the competing models. To qualify competing models, at least my own idea of what competing models are, other body on frame full size SUVs, like the Escalade, Denalie, Qx80, navigator, Sequaia, Expedition, Tahoe, wrangler unlimited.
I have driven X5s, Range Rover sport, M-class, g-class, grand cheeroke, durango. All unibody models, to me all cars made to look and function like SUVs as much possible for a car to do. The Range Rover and GC likely the most successful at it, at least on the off road side of things.
The seats are one of the things I like most about the current LX,LC, extramly comfortable to me on long trips.
One of the things I didn't like about the BMW, Range Rover and Benz and others were the hard seats. No matter how many ways I could move the seats, didn't make them any softer.
Interesting about seat support. I find soft seats to be nice at first but really not so great for long trips.
Maybe you aren't aware but the Range Rover and my LR3 both have what looks just like a ladder frame but also a fusion into the body. It is not really the same as the car-like BMW X5. Even more bizare is you seemed to lump the G into the unibody group. The G is more of a truck than any current Toyota including the truck itself if you consider the frame.
My LR3 can go anywhere with a current LX or LC, so could the Range Rover so off road capability is not really what I was getting at regarding "competition". Granted the LC/LX are a lot nicer than my LR3 but functionally inside there are some big differences in favor of the LR3.
I'd love it if Toyota could step it up a bit though as there are some aspects I really do prefer that have me seriously considering one.