aside from having more top-end power, the M104 has a better torque curve than the M103

the 94-95 W124s also had a better transmission, that started from 1st gear, and had smoother gearchanges. Overall topend gearing is also higher on these cars, for more relaxed highway cruising.

the 94-95 W124s also had better headlamps than the earlier cars, so you don't really need to convert to Euro-beams.

one other important factor is that the newer W124s had dual airbags.