
The frame twist was wild but put both trucks up here in salt territory and see which frame lasts longer. I would be willing to bet that the Ford frame will be in better shape in 20 years as long as you're not driving through crazy ass ditches on a daily basis.
Problem with fully boxed is water and salt get trapped inside and creates the perfect habitat to rust, when it's open it will dry and through natural occurrence will be rinsed off more. Tubing rusts from the inside out faster than any other form. That's why in the building trade angle, channel, I, and H are considered structural and tube (be it round, square or rectangle) typically isn't considered structural.