Common sense is the key. But because we are all human sometimes the common sense pendulum swings the other way too. In other words, covering up the amount of hours and focusing instead on the common sense aspect will probably point you to the more qualified of the two. In the case of the 777 captain and the PA-31, I would assume he/she would make a good call based on good judgment.

I'm not claiming to be an "old pro" in this industry, but I've seen people with very low flight time exercise very good judgment. I've also seen people with very high amounts of flight time exercise very poor judgment. Like I said before, we're human.