Thank you all for your replies! Real life intruded, so it has taken me a while to return to this topic.

The responses were a bit of a surprise. I anticipate replacing my W124 -- maybe! -- as it approaches 40 years old. I had expected some enthusiasm for models newer than the W210. Other than general comments on the usefulness of some of the newer technologies on safety and diagnostics, I found none. As I say, surprising.

I'll keep plugging with the W124, and see how long it lasts as a reliable daily driver. I don't drive that much, so it might be quite a while yet. And I will keep the recommendations here in mind.