new generation 30's and 44's can be found in all JK's (the 44 is missing in a handful of 07's) the differences between JK 44's & 30's vs. the old style is a larger pinion shaft, high pinion fronts with a bigger, larger housing, electric lockers, 1350 u-joints, and both axles can get disc brakes.
I think the spline is 32, but I can't remember off the top of my head. google the axle for all the specs, I can't commit them to memory.
what's so special about them is 2 things. the first is with aftermarket axle kits, these axles can be built with comparable durability and strength of 1-tons. the second and most exciting, they can be purchased to bolt right on a TJ. they're already sized and everything.