The newer car is probably the better choice because it has almost half the mileage. On W124, EVAP failure are common but not guaranteed. But, timing chain replacement is guaranteed at over 100k on these m119 engines. The timing chain costs about 2 grand to fix which will soon level the playing field between the two cars. The dark paint on the dealer car is a definite plus because a white W124, has too much black plastic trimming that makes it stand out. The groan could be the calipers and rotors need replacement but a tech will have to check. I would only buy the older car if everything that could go wrong was replaced. The m119 engine is one of the best engines MB ever produced and they seem to last 350k miles, usually. The older car probably needs a new set of dampeners and flex disc.