Depends. If the answer was posted within few seconds(in your case, it was within 10 minutes) it's completely up to the OP to delete it, or have it remain with information which will make it better than the one posted.

I don't see how this is a problem unless it's something like the same answer copy+pasted over an hour or so later. I wasn't the one who handled your flag, but I'd have marked it invalid if you asked me to remove the post.

Depends. If the answer was posted within few seconds(in your case, it was within 10 minutes) it's completely up to the OP to delete it, or have it remain with information which will make it better than the one posted.

I don't see how this is a problem unless it's something like the same answer copy+pasted over an hour or so later. I wasn't the one who handled your flag, but I'd have marked it invalid if you asked me to remove the post.

My point is given the timeframe of the specific question, it's reasonable to assume that both of you started answering at the same time. In general, if you see a bad answer, edit it. If you don't see an answer and while posting you were beaten, answer it, take a call to see if your answer can stand out on it's own.