As a sith, you get lightside points for not slaughtering people, slaughter being the norm. I can't remember the exact alternatives in the mentioned inquisitor choice, but it's usually a lighter shade of gray thing, but often mitigates another kind of harm. For instance, in that choice,
With the mentioned jedi choice, you're giving a hopeless man purpose and desire to keep on fighting the good fight. The alternative is to risk him taking his own life if you don't.