I have had continuous Mercedes car ownership since 1964. I had at least 25 different models. The car with the most consistent cold air conditioner was a '83 300SD. It was a white car with grey leather interior. You could hang meat in this car it got so cold. This car had the General Motors R-4 compressor, maybe not the best unit ever.

I would pick the 300SD over the 300 any day. Also do not downgrade the Climate Control System to A-134. Freon R-12 is readily available.