I'm not entirely sure about this, but I seem to recall that, should you choose to save your pet, you'd be punishable by law.
Again, it was a long time ago when this came up, but I seem to recall that the law requires you to lend aid to any person in mortal peril. Now, lending aid can be running for help. But "I was busy looking after my pet." does not constitute a legal defence, in this case. And no, your pet isn't a person sadly.
Now, I love my pet. I really do. But even so, I don't think my conscience could bear the knowledge that I let someone die. Who that person would turn out to be afterwards really does not matter. When you make your decision you're saving "a human being." Afterwards, whether that person turns out to be Mother Teresa or Hitler does not matter, when you made your decision it was "a human being". Whether your decision was an ethical or morally correct one does not change with facts supplied after the call was made.
Hence, I would *hope* I go for the person. But as I have never been in this situation or anything similar, I can't say with any amount of certainty.