I have one of each and echo what John said. Both are very nice rides.
To me, the 202 C230 is a economy car that rides like a mid-size, luxury car. It absolutely feels like a Mercedes. The fuel economy is phenomenal. It's balanced (but certainly not sporty) around town and very long-legged and relaxed on the highway. Other than the transmission issue John mentioned, the known problems are minor (mass air meter, AC evaporator temperature sensor, and a few others I can't think of).
1988 300 SL (5 Speed)
1994 E320 Wagon