You can do a variety of things. Most importantly, keep in mind that you can always upvote both answers! Keep in mind, the point of acceptance is to indicate the answer that you, the author of the question, found most helpful and/or conclusive to the problem you had. Also take a gander at this question, which dealt with a scenario where there were two answers that had different applications.
- Analyze the two and decide whether you liked the conciseness more, or the greater detail more. Pick the one you think was most useful in answering your own query.
- Pick the answer that sounds more interesting to you. Did one have a cooler detail than the other?
- Pick the one that came first, if that's your thing.
- Flip a coin.
- Accept one, and upvote the other. This spreads a difference of only 5 reputation. As far as which one to pick, see 1-4.