Neither...
While I haven't driven the 5.7, I can only imagine the amount of suck that would be. My work truck is a V10 Ford and my fellow worker has the same with the 5.4 V8. Both are later model 5spd auto with 4.30 gears, and weigh about 9500. The smaller engine is ok for in town but horrible in the hills, add a little bit of elevation and it can't maintain speed where the V10 plenty of power to spare (and runs in a taller gear as well).
Having a family member that owned an '04 6.0L PSD, personally pulled the turbo twice of the three times because of a stuck unison ring, replaced the egr cooler out of fear, plus a few trips to the shop for minor things. They make good power, well built truck, but that engine's emissions system is a time bomb. $5k to bulletproof from what I remember.
I'd hold out for a 5.9L Cummins, another V10, 6.2L Ford, or 6.4L Ram.