I understand what charlest is saying, and THEORETICALLY he is correct in the assertion that there are no bad balls, just bad matchups.
That being said, I would ammend it to this: There are no bad ball LINES, but you CAN have BAD balls ( that aren't manufactured "correctly") get out into people hands.
The El-Nino GOLD and the Lev-RG have been touted as wonderful by many bowlers, but NOT FOR ME. Even though I tried multiple layouts with multiple surfaces, NOTHING worked with those two. Does that mean ALL El-Nino GOLDS and Lev-RG's were bad? No, but I believe the ones I had were. Now, what was wrong with them? Nobody knows, but it had to be SOME reason they were absolutely DEAD from day one.
Maybe those of us who get "bad" balls are just randomly ending up with one offs that have some hidden problem that is never diagnosed by us or our drillers.
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"The difference between stupidity and genius is that genius has its limits."
Albert Einstein