This question has set me to thinking.... "what will all of us old time diesel lovers graduate to?" Or will we stay with the classic car forever? Having recently purchased a TDI, I offer the following comparisons and welcome yours:
1. Reliability - so far I like the MB because its virtually all mechanical
2. Performance - TDI
3. Longevity - Although some intial TDI's have turned 300k, I still sticking with the MB
4. Economy - TDI if I can learn to do the timing belt myself, otherwise it might be a toss up
5. Instrument Cluster Lights -

6. Indestructible - MB
7. Safety - MB
8. Alternative Fuels - MB
9. Tank Feel - MB
10. Seats - TDI
I'm still 80% MB for my daily drivers (4:1). Don't worry, I haven't cash all my chips in yet.
Don
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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)
SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed