Hard call. You already have everything for the older one. But I'm a fan for the 05+ because they're plentiful, affordable, and the aftermarket support is really getting good. I don't see a problem running unit bearings, they're plenty strong and simple to replace, most parts stores have them. As Chris said, My buddy Pearman is running ball joint with stock shafts. He's wheeled hard on 40" Stickies for a long time, still on the stock selectable hubs. When the shaft finally let go, he went ahead and upgraded it but he got lots of hard wheeling out of the stock setup.
I would sell the old axle, use that money to buy gears, locker and Artec truss and rock out. I installed a Barnes truss on a Chevy KP D60 with Chris one night, then 3 nights later turned around and installed an Artec Truss on the same axle with my buddy Curtis. Having back to back hands on experience I can tell you the Artec was miles ahead in fit an finish.