I'll probably get blasted for what I am about to say on the diesel fourm.
I have an 84 500SEL and a 91 300D 2.5 turbo. I drive the 300D as a daily driver and save the 500 for special ocassions like trips and such. Both cars are in very good condition and both run great. If however I had to chose one over the other, I wouldn't trade my 84 500SEL for two 91 300D's. The 500SEL is a great car, and worth the extra fuel cost.
This is just my opion.
And I still do love my 300D, just not as much as the 500SEL.

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84 500 SEL (307,xxx miles)