It seems all luxury cars have active suspensions now, so it's not a fair comparison to "non-active" cars. But I was recently driving a mid-2000 Mercedes E-class over the same roads I normally travel with an Acura TL and Mazda 6 of the same vintage and I was astonished at how smooth the ride was in the Mercedes.
Granted, I wasn't racing, so maybe the trade-off would be clear if I was plying each car at the track. But I'm not a passive driver, and the Mercedes did not have the "land-yacht" feel of older American luxury cars. It felt as connected to the road as the other cars, and I didn't notice more excessive roll or dive.
So what I'm wondering is: What accounts for the Mercedes' better ride? Is there something expensive that can be put in a non-active suspension that improves the ride without sacrificing handling?
My understanding is that all of these cars use the same independent suspension at the wheels, and the same sorts of springs and dampers connecting to their unibody. The particular cars I'm comparing even have roughly the same tire profiles. I'm assuming that since many tens of thousands of each model were produced that every advantage that could be "tuned in" without using more expensive parts would have been. So what could Mercedes, with more money, do to smooth out the ride that Acura and Mazda couldn't?