I looked at flatbeds for my F250, but the added storage capacity could not be utilized due to payload capacity.
When I went looking for bigger truck to haul a triple slide TC in the future, I found the 450/4500 class trucks were marginal at carrying the weight and mos likely over if towing a heavy trailer like mine.
This led me to the 550/5500 trucks. Utility beds were extremely heavy and expensive for my application. Since I was going to keep my existing TC and upgrade later, fitment was an issue. The most versatile option was getting a flatbed fitted with a SuperHitch and lower boxes. Once I get the larger TC, I will have appropriate boxes fitted to the upper deck or have enclosures on my TC along the sides.