I'm also contemplating (possibly) the same choice. Site searching netted me a lot of info, but only in bits and pieces. Here's hoping for input from our resident gurus, in the form of The Definitive MBShop Posts On The Issue, to which we can point others forevermore.
What are the weak spots we need to know about for an E-class six, let's say latter 124 through early next-generation (210, IIRC)?
What are the same for a 140 six, let's say through '95-96 or so?
Which is more likely to hand us huge bills, and for what? Once either one is well sorted out, how well can it be kept that way?
Our collective deep thanks for any light our experts can shed.
'97 SL500, 40th anniversary edition
'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)
SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)