Ok, I'll try one more time...I don't mean any offense, I just want to make sure you get the point.
Let's say for example you go to your local junkyard and they have a YJ identical to yours and they also have a '95+ XJ sitting next to it. You can pull the axles/ball joint out of either vehicle.
Most of the junkyards around here you either pay by weight or by what the part is. Either way you would likely pay almost (if not exactly) the same price for the parts from either vehicle. The only difference is if you pull the parts from the XJ you will end up with slightly upgraded parts.
So again, why wouldn't you get the upgraded parts in this instance? I'm not saying there's anything wrong with you buying the YJ parts if that's what you want, I just want to make sure you understand that BH's suggestion won't cost you any extra money, that's all.