One person being horribly tortured for eternity is equivalent to that one person being copied infinite times and having each copy tortured for the rest of their life. Death is better than a lifetime of horrible torture, and 3^^^3, despite being bigger than a whole lot of numbers, is still smaller than infinity.

I would solicit bids from the two groups. I imagine that the 3^^^3 people would be able to pay more to save their lives than the 1 person would be able to pay to avoid infinite torture. Plus, once I make the decision, if I sentence the 1 person to infinite torture I only have to worry about their friends/family and I have 3^^^3 allies who will help defend me against retribution. Otherwise, the situation is reversed and I think its likely I'll be murdered or imprisoned if I kill that many people. Of course, if the scenario is different, like the 3^^^3 people are in a different galaxy (not that that many people could fit in a galaxy) and the 1 person is my wife, I'll definitely wipe out all those assholes to save my wife. I'd even let them all suffer infinite torture just to keep my wife from experiencing a dust speck in her eye. It is valentine's day after all!