As stated, they both do the same function. I use air level in places where jacks would possibly sink in. Some grass lots, asphalt, or wet conditions on dirt.
The air will automatically re adjust every 30 minutes. The biggest adjustment is the first one as the air was much hotter on the first fill then it will be once everything has cooled down. Still during temp swings it will adjust, as air volume will change.
In my coach if the high point is either rear axle, then that will be resting on the frame and the other bags will inflate. Under that condition there is no bounce.
If the high point is the front, then the rear bags have air and you notice a bounce. With kids that bounce is noticeable, as well as the washer on spin cycle.
Also as stated, hydraulic give far more range, but that can be bad too...think wheels off ground!
I use them both.
It is not for in motion driving, that is a different function run by a different "system". But it does allow for ride height overrides, at least with active air.
2013 Newmar 4347 DSDP * All Electric *HWH Active Air System * Upgraded Front Heater * Lots of tweaks and customizations - See Blogs
NHSO (Newmar Hoot, Sevierville Original), Kindness Matters