Assume opponent's not on a foul and that the thirteen ball is not dead into the bottom corner as you didn't say so.
The two best choices are a) to concede the straight fourteen ball or b) to graze the five to leave the cue ball near the long rail.
Conceding the long straight fourteen is a much better choice. If you graze the five, you risk having your opponent leave you pinned to the three ball, creating an underneath threat with the four ball. The key here is that the eight and four are frozen to each other, making this safety quite easy to execute. Fall into this trap and you'll be way behind in the safety battle.
Of course, grazing the five may or may not leave the response described, but it's a risk worth avoiding. Even if you deny it, you might leave opponent a similar shot that would pin you to the six ball and bring the fifteen into play, which also means trouble.
Nice thread. If you want to be a good 14.1 defensive player, you need to learn how to deny aggressive responses to your safeties.