The reason why makers offer a heavy half and a max tow package with slightly higher payloads, is that people use these trucks as "daily drivers".
I was all ready to buy a F250 but was stopped in my tracks when I found that the 2016 F250 Screw 4WD 6.2L w/3.73 Locking differential was only getting 10 mpg city, 15/16 mpg Expressway and 12 mpg mixed. I simply can't afford to drive a truck with that bad of fuel economy as my work commuting truck.
My 2016 F150 Screw 4WD 5.0L w/3.73 locking differential is getting 18.5/19 mpg mixed and 22 mpg expressway. I don't drive city but I'm thinking around 16 mpg.
When you add in the HD payload package you lose about 1.5 mpg due to the extra weight of Ford's thicker F150 frame, the other components and the heavier LT tires. Still much better fuel economy than the F250. Plus with any of the engines, the 5.0L or 3.5L Ecboost or 2.7L Ecoboost, you'll get a much more powerful truck as the 6.2L just doesn't offer the power for such a heavy F250 truck.
The F150 heavy Duty Payload package truck doesn't have the tow capacity, or hitch rating that a F250 has, and doesn't have the variable snow plow compatibility that the F250 has, but for people who want "1" vehicle, the heavy half ton does great.
Even so, my truck without the heavy duty payload of around 2300 lbs, has 1890 lbs which is enough for any of the trailers I would ever purchase for my family. So I stopped looking for Heavy Duty Payload trucks that I was going to order. My truck pulls my trailer good even without LT tires but if I towed more, I'd definitely get those LT tires.
My truck is about $2K less than the F250 I was looking at but since there were few with my needed options, the F250 was slightly better options to account for the extra money where MSRP is concerned. The F250 also didn't have the rebates that the F150 did so it's total cost was about $4K more.
Now when you consider apples to apples, and put a Ecoboost with Max Tow package in my truck, along with the Heavy duty package and match them closely in option, their final costs after rebates and X-plans were within a few hundred dollars of each other.
But the F250 still came out much more expensive in operating costs per month especially with fuel.
The F150 that's optioned right with good payload is hard to beat. The new Chevy Silverados are also very close in towing and payload to the Ford F150s.