I get every type of sick there is whether it's car, sea, ride, swing, even airplane sick! Soarin has never made me feel ill. Never done mission space though for that reason.
My experience is you can want to enjoy something until the cows come home, but if your body disagrees there's very little you can do... don't jeopardise the whole day.
I found flight of passage made me slightly queasy, I would say FOP is more intense than soarin IMHO.