Don't worry - there doesn't seem to be an appreciable difference in carb levels between 12 and 22 oz, I always use the same amount of priming sugar. The 22s can take a little longer to carbonate sometimes, but it's not a given. Much of the time they're ready at the same time as the 12s.
I think the reason Party Pigs and kegs use less priming is not because they're larger, but because they are dispensed while maintaining pressure - bottles lose the pressure as soon as you open the cap.