Mercedes have detailed tables on spring ratings for various individual models according to equipment fitted so theoretically the best- but as models age I suspect this gets more restricted to possibly 2-3 choices? It might help to check the existing springs for colour codes and spring pads for the number of pips which are indicators of their thickness.
Your choice may be limited by cost and availability whichever way you decide to go. In terms of quality I doubt there is much between them- Mercedes don't make springs so the MB ones may well be SACHS or LESJOFORS made for MB anyway.