Ive got an 82 300d and it rules. I prefer the diesel Benz over any others, they are a little bit easier to find parts for in the w123 body style. A turbo is nice too. I would personally never get an sl, isn't as great of a chassis nor are parts as easy to find. They made the w123 body style from 1973-1986 and it is buily like a tank. The sl is not really a sports car and not super luxurious, kinda in the middle somewhere. Though if you are willing to learn to fix it yourself and scour the scrap yards they can be super cheap. Expensive parts are things like the window regulator/motor, transmission bits, vacuum Regulator and fuel injectors. I re-did the entire front end suspension on the 300d with new shocks, tie rods, drag link, damper, ECT and it was less than $500 in parts and only took a few hours. Pretty simple cars and they just keep going and going forever. Setting the valves is a yearly thing and keeping the oil fresh will help everything be happier.