Tell your prospects that your product is so good that you in fact have written two different sales letters. Your prospects will have a choice which of the sales letters they want to read, or they can read both of them.
The reason why you have written two different sales letters is because one of the letters may persuade them to buy more than the other. You have two completely different letters, one better than the other, it all depends on who reads it.
The best thing about this marketing strategy is that it’s like you’re giving your prospects an option on how they want to be persuaded. If they don’t like one of the letters, they can read the other one and it might actually persuade them into buying. If you only had one sales letter, they might not have bought your product.
Now, you only need a way to tell your prospects why you have two sales letters instead of just one. I think that the best reason is that your product is so good, and there are so many words that can describe your product, and there are so many reasons why people should buy your product; you just had to write (at least) two sales letters to be able to fit all your thoughts about your product.