Okay, maybe this is a dumb question or maybe this is like having "overdrive" on an automatic transmission in the 90s... what's the difference between the "comfort" and "sport" settings on my suspension?

I don't really notice much of a difference when I switch between them... but maybe it's just me.

I don't think there is a change in suspension setting unless you have airmatic suspension option.
The only change as far as I know is with transmission shift setting change.

I do have the airmatic, sorry for not clarifying that earlier... i'm new to MB so unsure of what features are standard on certain models etc

in comfort ride height is higher when you hit sport its lower

Actually, the Sport mode changes the damping to a much more aggressive and stiff suspension. I have taken the 550 to a track and you can really feel the difference in the turns. On a twisty road you can tell the difference between the normal and sport modes. On the straight highway it only accentuates the rough road. I would not leave it in sport mode, as it will wear out the airmatic suspension quicker and potentially cause a component failure. Nobody wants that.

isn't it stiffer in sport mode cuz it lowers tge car? thats why it might feel this way.. no?

I do not believe the car is lower in Sport mode. It automatically lowers at speed to reduce drag and improve mileage and performance, and then raises back up when slowing. I believe the Sport mode only increases the damping effect of the Airmatic system.

According to the manual, it effects both height and tuning. See pages 191/192 here. The height difference should be obvious if you stand outside or what how the star on the hood moves against a fixed option while you're parked. Sport is 0.4 inches lower than comfort and + mode is 0.8 inches higher. At highway speeds, you will be at sport height whether or not comfort or +1 is selected.

I haven't heard before that driving in sport mode would wear the components faster. However, I can see how sporty driving habits would wear out suspension components faster.

on point