Bed Length = Personal Choice
As others have said, it is TOTALLY up to what you are going to possibly use the truck for. I have had one short box, and had fun climbing in the hills with it, hauling my trail bike around, and occasionally wished I had the long bed. This was when shortbeds had to be half tons (75). Long beds since. As I wanted a heavier truck, the short bed was not an option when I got my 95 PSD (yeah, big mistake, I know) The diesel was not available in a short box by Ford until 96 or 97, so my decision was made for me.
Now that I had a choice in getting my CTD in 2003, I opted for the long bed. I didn't even consider a short bed.
Reasons for my choice of a long bed:
1. Having towed the same tag-along with both, the long bed was MUCH more stable in both side sway and vertical movement.
2. Having a 35' 5'er, we wanted a Dually, and that stabililty both ways.
3. While getting a slide in camper is not currently viewed as an option, it is not TOTALLY out of the picture, and I would want the long box not only for the CG to be forward of the axle, but not be limited to shorter slide ins.
4. The occasional load of lumberyard or dump run. . I have a toolbox behind the cab that takes up enough in the long bed.
5. If I ever get a quad, I better get 2, if you catch my drift.
Different strokes for different folks, but I never once regretted going with the long bed..... for OUR purposes...