The ride is the same.

A little more tire noise in the W210 (ContiTouring Contacts on each car), but the W210 seems to corner better with less roll. The steering can be a little numb however, and doesn't seem to provide the feedback of a W124 at higher speeds (in excess of 100 mph). Its a bit of a challenge to point it in the direction you want it to go every split second on an uneven surface.

They're both nice cars. The 210 is somewhat in a league of its own for space however, considering how much better the interior is carved out. The 124 is really cramped!