My feeling is the RX is more capable offroad than the IRS expedition. Take a look at the ground clearance under the rear IRS crossmember. It seems less than that on an Accord. Unbelievable. I guess they have to make it that low to get the center of mass low enough, as the thing looks top heavy otherwise. Ditto for all the Expeditions vs. the Toyotas (RX, 4runner, LC/LX), which seem to have ample width for the height/size.
Back onto topic, driving the LX feels like driving a tank or motoryacht while the RX feels like a normal car. It's comparing apples to oranges. Still, I know my wife would love a RX as a DD if we had one. But when we buy another car to eventually replace the '86 4runner, it'll likely be a FJ Cruiser w/ 6spd manual (mostly because it's manual, also because there are lots of mods available compared to the 4runner).