During the 2002 model year, DC (well, probably Dana) did away with the center axle disconnect on the Dana 60 front axle. The majority of '02 trucks do not have a center disconnect. This means that when you are in 2wd, your front axle and front drive shaft will turn. The nice thing is, when you pull that lever, you're in 4x4 guaranteed. Downside? Can't go the 2wd low conversion.
As stated above, DC did away with passenger side grab handles, underhood insulation (although you can put this in yourself), and some other small things.
My opinion? If the trucks are dead even in your mind as to which one you would want to own, I'd base my decision on this: If you want interior goodies and hood insulation, go with the 01. 5. If you want a 4x4 system that won't leave you stranded when you have vaccum issues, get the 2002.