The premise itself doesn't make sense unless you think the only possibilities for supernatural deities are 2 evil beings, so the question can't really be answered, it's like choosing death by drowning or hanging.
A god that wants worshipers, or puts a gun to their head to submit to him for his own pleasure is obviously immoral, so I would question his definition of hell as being a place of permanent torture. Being a slave to a higher authority for all eternity is torturous as well. If he's supposed to be the 'good' guy, but he isn't, then I would say 'maybe Satan is actually the good guy and this guy is lying?' and try to find out.
If he was able to prove hell really was a place where you were burned to death over and over, then I would have to compare that with whatever heaven was. Heaven doesn't exist so I don't know what it would be except the idea that you would be a slave to someone forever, and we don't know what all of that entails.
It's an unanswerable question without more details, we can't just assume that heaven is ruled by a benevolent dictator and whenever you're not praying at his feet you can go on roller coasters and shit, which is better than being tortured over and over all day. That's all in our heads.