disco and nondisco

i have an o1 xj with a d30 up front and a d35 in the rear, i want to put the better d30 in the front, which i think is the high pinion axle. i also want to go with the 8.25 or the ford 8.8 with disc brakes. but my question is. i don't understand the difference between the disco and the nondisco front axles, could someone educate me please? thanks

stickied at the top

http://www.naxja.org/forum/showthread.php?t=70422&highlight=axles+for+rocks