If you're wanting to swap in a 60, look at the 99-04 Ford Super Duty ball joint 60's. They make the old KP 60's look like child's play.
Personally, I wouldn't want either option you mentioned.
I think you meant 05+..............they are 35 spline throughout with bigger balljoints etc. Extremely strong!! 99-04 are strong but only 30 spline outer but there are options for 35 spline and options for a lot of things. The hardest part of a balljoint axle is steering as high steer is easier on a kingpin and some people rather have the easily serviced kingpin axle as the hub assemblies on balljoint axles can get pricey. Either way its kind of a toss up but if you are running coils there is more room to run coils on a kingpin axle. On a balljoint front there would be a lot of casting to cut off and limited room for coils and arms, but its been done. Plus the center chunk is farther out of the way of the engine allowing more uptravel than a kingpin style axle.
Here is the casting cutting I was talking about.........
05+ are great axles as well, I was planning on building a hybrid fab 9/05+ SD60 axle last year but I doubt that'll end up happening. The 99-04 stuff is more plentiful and is what companies like Currie use for their applicable outer components. When the 05+ stuff starts getting more aftermarket attention and some of the current parts start to drop in price (high steer arms, drive slugs) they'll be a much more viable option.
I still think it's worth the time to look into a SD60 axle instead. The casting isn't difficult to section out of the way and the axles are just so damn big and strong compared to the KP stuff.