Sorry, I don't know the answer, but one thing I can say is that running changes certainly did happen throughout the course of the vintage line, so I am not surprised to see two different versions of the bomb. I have however also seen fake Y-Wing bombs for sale before now, but if you have owned yours long enough to pre-date the fake market, you can be confident they are genuine, but as for which one came first, or whether one belongs to Kenner and the other Palitoy, I'm afraid I am not knowledgeable enough to say.
With luck, hopefully someone with more knowledge than me will read your question and give you a more certain answer.
Jeremy