I find it hard to believe rear air shocks won't affect the ride quality vs springs. Maybe not in cornering, but I bet you'd discern a noticeable difference on rough pavement (less bucking/bouncing from the rear springs).
I ordered mine with the 3rd Row Package because I'll be towing a 4500 pound boat up and down big mountain passes in the summer and the self-leveling suspension gives me piece of mind.
I have full self-leveling, height adjustable air suspension in my LR4 and absolutely love it--I will never go back to a fully sprung SUV or truck again. The ride quality on air shocks is sublime.