Tough choice. I'd have to go with the cat, because, as sad as seeing an adorable furball die is, I'd rather see it go than 100 people.
Well... I guess it's dependent on which cat and who the 100 people are. A large percentage of the world are jerks, but a vast majority of those turds are curable. So, a simple random sample of 100 individuals would undoubtably include several jerkwads. Law of large numbers. However, of those jerks, there maybe only one or two, if any that are incurable with modern medical science.
Wait, there is no cure for being a dick?