At least for the W124 wagon, I can tell you that H&R, Eibach, MB SportLine, and Brabus springs are all different at least in height. However, I don't know the spring rates.

The H&R are VERY short, and perfect for the track, but not the street. They do look the best.

The Eibach is between H&R and MB Sportline in height.
The Brabus is specially matched to Brabus self-levelling struts.

Hope this helps,
:-) neil