The M103 177hp 3.0L six in the W124 is preferable to the 2.3L 130hp M102 four cylinder. Not that the M102 is a bad engine, but the 300E is a very well balanced car with excellent performance and terrific durability. The fuel economy penalty is minimal between the two, as the M102 has you mashing the loud pedal with more force.
One nice thing about the four is the extra room in the engine bay for DIY guys.
Also, in your nation do you have taxes based on engine size? Could be a factor...
1998 C230 "Black Betty"