You can always delete your answer unless it's been accepted, but usually you shouldn't.
Your answer may still be useful, even if it isn't the best. You should only delete your answer if you think it's just noise (for example, because it's completely wrong and no amount of editing is going to make it right short of copying another answer). If there's useful information in your answer that no one else has posted, or if you think that explaining it your way may help someone, do leave your answer.
Having multiple answers is how Stack Exchange is supposed to work. On a healthy site, the average number of answers per question is typically somewhat above 2 — note that the variance is huge, since that includes both popular questions with many answers and unanswered questions.
(Note: I'm speaking in general, I'm not saying anything one way or the other about this particular answer.)