Just read the the factory MB 1992 Introduction to Service on the 400E and 500E and would like to share the following regarding suspension:

400E & 500E:
Tightening torque of the pinch-bolt & self-locking nut for the damper strut-to-steering knuckle assembly was increased to 200 Nm. The two lower hex bolts are unchanged at 110 Nm.

Both receive different buffers/bumpstops on the stuts: 500E: 70mm/bone color; 400E: 83mm/red color

500E:
Damper strut is equipped with an extension limiting spring giving additional vehicle support during cornerning, hence the smaller diameter swaybar.

500E self-levelling struts also has an extension limiting springs built-in.

500E struts are also shorter in length than the SportLine struts. SportLine is definitely stiffer.

Here's some pictures of the 500E strut/damper (short) and the 300E SportLine strut/damper (longer). Both are made by SACHS.

I don't know if the Bilstein Sport front dampers/struts have the built-in extension limiting spring, but they do have the shorter strut length like the 500E's.

Enjoy,
:-) neil