I have a 1993 W124 with the M104 engine (3.2 liter) that was carried over into the current body style in its first two years (96 and 97), and a smaller version of the M104 engine (2.8 liter) was used in the 94-97 C280.
I agree with blackmercedes in chosing the current V6. It's not that I dislike my engine, but its true that this engine suffers from oil leaking from the head gasket about every 100,000 miles or so. There was a also a problem with the wiring harnesses. Like the inline 6, the V6 are proving to be very reliable. They don't have the long-standing history of the inline 6's, though, so only time will tell.
The only problem with getting the V6 is that you have to buy a 1998 or newer C-class or E-class, which is big bucks, at least $20,000 or more. However, I'm not sure that the average buyer knows that there is an inline 6 in the 96 and 97, and a V6 in the 98 and newer. It doesn't seem to cause really any difference in the resell value. The used car values are all about mileage, year, and condition. In other words there is not a huge price bracket with the 96 and 97's at a lower price bracket, and 98's and newer at a higher price bracket.
You can find many examples of late 80's and early 90's E-classes for under $10,000, and 93-95 E-classes in the low to mid teens.
The differences between the W124 and W210 E-classes, as well as advantages / disadvantages between the inline and V6's has been discussed sooooo many times on this site, if you do a search, you can spend the next 6 months of your life reading up on these topics.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".