My personal opinion on air suspension.
First, I have had several vehicles with it
1987 Lincoln Mark VII LSC with 130,000 miles (back in 1992-1996) and loved it, it did have issues, with control valves, and compressor. But had built in diagnostics, and I repaired the compressor for free, and replaced 2 valves for cheap (under $30 each I believe)
2012 Jeep Grand Cherokee Overland with optional QuadraLift with 100,000 miles for a year, no issues at all, would not buy another without it, loved the ride and versatility. Lowered for park/entry/exit, all the way up to aero, normal, OR1 and OR2 over 4" of total travel.
2021 Jeep Grand Cherokee L Summit (Bought new last summer) with QuadraLift, same as the 2012
I had a 2018 S90 Inscription T6 without it, and 18" wheels then shortly after trading that on the 2021 Jeep I got this 2019 S90 Inscription T8 with 20" wheels and with rear air suspension.
I would say that 2019 with 1" less sidewall rides smoother/nicer than the 2018 for sure, if I had the choice between 2 otherwise identical vehicles, I would always choose air suspension when possible.
But, (everything before "but" is B.S.) I would not actively search for a S90 with air suspension as a mandatory criteria, it is nice to me, very nice, but I could live without it easily, and if that meant saving money also, all the better.
Also I would definitely put it in the negative column on a very high mile older car without a warranty, even though I knowingly bought the 2012 Jeep with it, mainly because if/when it fails on a Jeep, there are probably 100x more of them both in junkyards for cheaper parts, plus much much more online support if needed.
Now on the XCs with it being also off roady type of feature, like the Jeep, I would want it. Basically 4 wheel, yes I would desire it, rear only, it would be nice, but not required.
P.S.
Also, I had rear air shocks on my 1967 El Camino (also factory) that I was automating before I sold it 2 years ago, with factory 1970 parts!