We have owned both as well .
I feel the most noticeable difference is noise and ride .
We can ride along in relative quietness and talk with out yelling .
We also still use our in motion satellite tv and can actually hear it
You may be expecting to much out of an exhaust brake , it may not
perform any better than the braking effect of a gas rig , after all
the diesel rig is usually quite a bit heaver .
The more expensive coaches will have an engine brake ( compression )
now that is a real brake , it's what the semis have .
Performance of gas rigs of recent yrs is much better than the old
carburetor engines so don't assume the diesel will out perform it
Diesel coaches drive and just feel different , a little slower revving up
and air brakes feel different too
You probably should drive several of each and see which suits you .