If you are going to replace both shock and spring (recommended), I would go with the Sachs. Replaced mine about six months ago; much better ride plus no squeak/creaking. These come as a unit.

If you want to replace shock only, I would go with the Bilstein. The Bilstein is the better of the two. I put the Bilsteins on the front of my ML, very nice combination with the new rear Sachs assemblies.

If money is no object......new bilsteins all around with new springs in rear. Cost and labor wil be higher........Just my opinion......