Sorry for the terrible pics, but if you use the bed for anything other than groceries the 8' part is awesome! In the 5th wheel pic i have enough wood in front of the hitch to last a week of camping as well as my weber gas grill, with room to spare behind the hitch for other items. In the gooseneck picture, i have another 40 cases of pergo flooring in the bed of the truck on top of everything on the trailer obviously.
If you do any sort of towing, the added stability of the longer wheel base really comes into play. In a cross wind the truck is way more stable due to the longer wheel base, it also provides a smoother ride overall in my opinion.
My folks run a similar truck (dually crew cab long box) and they have a 60 gallon aux tank / tool box combo in front of his hitch with room to store more items in front of the hitch.
My overall opinion and impression is I will not own another shortbox, just not worth it. Sure it's easier to park, but i always park in the back away from anyone anyways. The added length to get full sheets of plywood, drywall ect inside is huge...
Also, i've never heard anyone say they regretted buying a long box, but you hear a number of comments from short box owners wishing they had gone long box...