You nailed it!
I also have a 87 300TDT and a 97 E320. I got the 300TDT after I got the E320. Now the E320 is in storage and the 300TDT is being enjoyed. It shows so much character, quality, and rigidity.
I summarizes the handing of the W124 and W210 as follows:
(It is not an equal statement but more of a trend statement and I have driven both other vehicals mentioned).
The W124 is more BMW-like. Good handling.
The W210 is more Cadillac like. Good comfort.
Some people buy their new W210s and then replace all the brand new shocks.