If you haul a lot of tools or timber you may appreciate having the 6 foot bed w/ the xcab. Also the xcab gives you a little more interior room to put stuff you dont want in the elements. But its no good for people.
Personally Id go w/ the dcab and get a trailer if i needed to haul something that wouldnt fit in the bed. The nice thing about the dcabs is you have a lot more room to stow junk you dont want in the bed and also fit people back there.
I have an xcab BTW. I like the 6 foot bed as I haul alot of crap when I go hunting, 3-6 deerstands, clothes boxes, 2 coolers, a few deer
all fit in my 6'. I wouldnt survive w/ a dcab bed. Id have to get a trailer. But I might could end up putting the clothes boxes in the back of the cab.
Bottom line Id go w/ the dcab. The only thing that I dont like is that the years i like (98-04),(im not into the new tacos(yet?might happen)) dont offer a manual in the dcab. which was only offered 01-04?