The BMW has plenty of low down torque (5th gear at 30 is no problem, quieter and more refined than a diesel too), but with responsiveness a diesel can't match. Then as the diesel runs out of puff, the exhaust valve on the BMW opens and you're treated to a classic straight six howl and feel like you're riding a wave that's getting faster and faster all the way to the redline.
The 3.0HDi is definitely one of the very best diesels at the moment...and you can even get a 270BHP version from Jaguar. But it is an engine that does suit the C5 / 6 and actually one that's better with an auto 'box (I tried a C6 recently and was impressed, however see my comments below).
I don't disagree...but given that in the US you don't have to worry about fuel prices, I'd rather drive something that's more appealing to an enthusiast.
The way I see it is that diesel engines are a compromise for people who use their car as an appliance and see it as no different to the white goods in their kitchen. However as an enthusiast, given the choice I'd always choose a good petrol over a good diesel...
...the best way I can explain it is like this: A diesel engine is like a nervous teenager in their first sexual encounter - a shaky start (below say 2k rpm) before suddenly everything is delivered prematurely and they run out of stamina when you want them to keep going! - It's a disappointment and not a good experience when compared to a petrol that starts off responsive and builds into a thrilling climax.
Do you mean to tell me that if you didn't have to worry about fuel economy you'd prefer a diesel? Even in something like a Lancia Stratos (which IIRC you said was one of your dream cars)?
Personally, I'd like all non-enthusiasts to move onto driving electric cars as the technology matures, leaving us enthusiasts with a more plentiful supply of super unleaded.