Coil owner here - I don't regret it at all. I love gadgets, and think I'd enjoy playing with it sometimes, but that's it. The coil suspension is terrific.
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My son says there is a difinite stiffer ride when sitting in the back of a loaner with springs. Twice I had to drive on dirt roads and raised the suspension to the max. I also am able to adjust the height making it easier for the in-law to get in and out. I've also had to raise the car when going in and out of a couple of steep drives.
Unless you're driving two identical cars back to back I wouldn't trust the subjective rear-end test with respect to stiffness. Just my two cents, but I think they're actually pretty similar. I did two test drives in the same day, one air and one coil and didn't notice until he told me the 2nd car had air and I should try adjusting it.
With respect to ground clearance, it adds 1.3" to the normal height under 10 mph. That could help going over a curb, or driving really slowly off road I guess, but 1 inch isn't turning this into an off-roader
And again, it's only an inch to help getting in or out easier, that's not super substantial IMO.