I think one of the reasons I finally chose specks is because the unlike implied, the suffering does not simply "add up": 3^^^3 people getting one dust speck in their eye is most certainly not equal to one person getting 3^^^3 dust specks in his eyes. It's not "3^^^3 units of disutility, total", it's one unit of disutility per person.

That still doesn't really answer the "one person for 50 years or two people for 49 years" question, though - by my reasoning, the second option would be preferrable, while obviously the first option is the preferrable one. I might need to come up with a guideline stating that only experiences of suffering within a few orders of magnitude are directly comparable with each other, or some such, but it does feel like a crude hack. Ah well.

If statistics are being gathered, I'm a second year cognitive science student.