I love everything about a W126. I am planning to add one to my collection of cars. I will probably buy a 300bhp euro version - I'll import it myself.
The W140 is a strong looking car, but big and heavy and bulky. I find the quality not as great as the W126. I'd still own one
. I'm scared of the evaporator repair though.
First chice for me would be the W126 and it will not depreciate anymore and 55,000 miles - that's super low mileage. I hope the color is nice.
Good Luck