Check out these two posts:
http://www.peachparts.com/shopforum/showthread.php?t=19772
and
http://www.peachparts.com/shopforum/showthread.php?t=134501
I do love both the W126 and the W140. There is no denying the W140 is years ahead in terms of technology, ride comfort, sheer size and equipment. Although, I think in terms of design the W126 is a much classier statement.
If you really don't mind spending a few thousand bucks a year for maintaing probably what could be the best car ever mass produced, go ahead and get a W140. You will definitely not regret it.