I think the Cummins sounds great. Id take a 6BT 12 valve cummins with mechanical fuel injection over any of the newer ones. You can run biodiesel in these with no ill effects. Plus with an un corked exhaust on a standard shift one they just sound bad a$$.
Power stroke doesnt sound good at all to me. Sounds like a coffee can full of rocks shaking around at idle, and i wouldent give ya a dime for the GM Izusu sourced duramax.