LOTS more power. The DD16 600 was pretty much on par with the MP10. My friend has both in his log trucks.
And for some odd reason, at least in 2020 when I quit trucking......Detroit will only give you 1650 or 1750 torque now with a DD15 but will give you 1850 with a DD13. They had discontinued the 560/1850 DD15. Maybe that's how they were trying to lure people into a 13 litre??
And having ran both of those, 505 h.p. in a dump truck/pony at 140,000 pounds, I can say the DD13 was stronger, but the DD15 had more bottom end lugging power even at only 1650 torque.
From a dead stop, the DD15 505/1650 could out accelerate our ISX 550/1850. Same gears, tires, transmission. And it would outrun it up the hills until you made that downshift into low range on the 18 speed.....then the ISX would disappear.