Both the 300E and the 190E 2.6 have the same M103 inline six, which is smooth, but somewhat troubled by headgasket failures. As you can imagine, the lighter weight of the 190E makes the combination a bit more potent and there are many more 5-speed manuals in the W201 family than the W124 if you are so inclined. To get the same peformance in a W124, you'd have to go to a 300E that has the M104 twin cam inline 6.