The W124 (google or wikipedia about it) is considered the "last true" Mercedes that had went through a LOT of crash/safety test, VERY solid build. After 17 years, my car still looks like new (both interior and exterior). It's amazing! If you look at YouTube and search for "Fifth Gear's W124 Built Quality" you will truly be amazed! Maintenance can be a bit costly, but if you know of a good mechanic you should be fine. Highly recommended!!
Solid build, exterior paint quality (feel like last forever), interior (simply luxurious), ride comfort,
a bit better acceleration maybe? better AM/FM factory radio