I think you need to refresh yourself on the horsepower equation: HP = (Torque * RPM)/5252.I wouldn't bet on it... the 3.0 has 250 hp @ 3250 rpm and 440 lbft @ 1750 rpm. The 3.5 has 375 hp @ 5000 rpm and 470 lbft @ 3000 rpm.
The 3.5 makes roughly the same HP in the lower RPMs as the 3.0 and then makes quite a bit more as the RPMs rise. While the 3.0 makes its TQ down low... that's literailly all it has to offer.
I haven't seen anyone do calculations specifically for the 3.0 v6 diesel, but if its making more torque at a lower RPM compared to the 3.5l ecoboost, its likely making more horsepower at that lower RPM as well.
The 3.0l diesel doesn't way 1,000lbs more than the 3.5l ecoboost. Ford could likely boost the payload if they desired to do so. Cost is relative. You might pay a little more for the 3.0l diesel in the shortrun...you might quickly recoup the added costs if you're doing lots of highway driving and/or towing.The baby power stroke also has about 1,000 less payload due to the weight of the motor. When you add in all the cost, the 3.0 is the most expensive option to drive per mile.
Though I will say that I find the cost argument less and less logical in this day and age. People think nothing of modifying the crap out of their F-150 with bigger tires, lifts, ECU tunes....all of which degrade mpg's. Or people will daily drive gasoline Ram 3500's or F-350's to and from their office jobs. But those same people will swear away diesels because of the added "costs." Makes no sense...