Duramax, definately the quietest up until '03 that I've heard.
Topwater, you care to comment?
Also, less of that "shaking chatter" during idle than other recent deisels.
I understood that before it became available in the light truck market that it was used commercially in Isuzu box van chasis, and had good feedback as far as the reliability, economy, and so on.
I wouldn't call any deisel "small" in a truck, but can't deny small fuel consumption (and big power). Or cheap.
I've R' and R' enough tranny's off of that 6.0l Ford to know that I wouldn't spend my money on it. Plenty of power, but that's why I said Cummins over Powerstroke earlier.
My old man was a deisel mechanic for 20 years and he'd say GM w/duramax. He's actually been contenplating signing his life away on a new one for months, but has yet to bite.
Myself, I'm not in the market for one, but those deisels are comparitively quiet.