I wouldn't say one or the other is BETTER, just depends on the quality of parts used. I mostly use ball/ball but just put a set of "cup" pushrods in an 865" motor. Now of course those pushrods are so big, that basically the "cup" is machined into the pushrod, but it is still the same thing.

Now I will say, that in the case of a standard 3/8 pushrod deal, I prefer ball/ball because the pushrods are one piece and you can get them in .180 wall. That is a STOUT 3/8 pushrod, plus places like Comp and others keep them in stock at virtually any length you need in .050 increments

Monte