I asked this question and received two contrasting, but equally valid answers. I don't feel it would be fair to choose one over the other, so what is the right thing to do?
First of all, if you feel that an answer is helpful, you should upvote it. That's easy because you can upvote both of them.
Next, you can choose one as the accepted answer. That's an indication of this worked best for me.
You're under no obligation to vote and accept quickly, so just take your time and see what works. You can always come back later and put the check mark where reality determined it. (Or don't accept any answer, in case none are right for you.)
The sum of votes by all users show the trend of what the majority feels. The check mark is your choice alone as a way of giving an extra thank you to the author. If two answers are exactly identically useful, well, you'll have to pick one. Nobody gets upset over not getting that check mark - we're adults and we can handle it :-)