The GX is a body-on-frame SUV and the TX is a unibody crossover. Both have their advantages, previously detailed.
Lexus stuck to the ladder frame design of the GX because it still needs to be a proper off-roader. Land Rover has proven that a decent off-loader can be built without using the ladder frame method, but the ladder frame method is superior in terms of wheel articulation, traction and overall robustness We cannot deny that.
Unibody vehicles like the TX are lighter, stiffer, cheaper to manufacture and have a lower center of gravity. Unibody vehicles also tend to be safer because cell deformation is more predictable. Also, the body itself isn’t individually shuffled along the frame below, which usually makes for a nicer, more refined ride.
I’m not saying one is better than the other, but it’s clear that when Lexus designed the TX, they were willing to sacrifice off-road performance in favor of comfort and stiffness. Lexus specifically mentions adding welds and glue to his existing GA-K platform to provide a more engaging driving experience.
https://carbuzz.com/features/whats-the-difference-between-the-2024-lexus-gx-and-lexus-tx What’s the difference between the 2024 Lexus GX and Lexus TX?