Depends on what you're buying the book for. If you're buying it just to read, I would go with the corrected text edition. That edition will have what typographical errors were not fixed in the first printing of the book made. Sometimes there is no time (or money) to fix it the first printing, so publishing houses often make what we call "reprint corrections," to ensure that the text is as perfect for our readers as possible (no matter how many printings it takes!).
If you're buying the book for profit, I suggest getting an uncorrected edition, especially if it's a Faulkner. If you can score a first edition, even better. It may not have value now, but it may later on down the pike. For example, the bound galley (selling materials used by the sales force, which using the not-final text) for "To Kill a Mockingbird" by Harper Lee sold SIGNFICANTLY more money than the first edition, first printing of the book, simply because the bound galley had MISTAKES in it that Harper Lee made but which hadn't been corrected.
Just a thought. It could be that the book won't gain value till you're old and gray, but you should check on eBay if there is even a call for it. If not, heck, go with the uncorrected edition, anyway. I findy typos annoyingly charming.