Although I can see why once you do begin to invest and contribute you can begin to really solidify the addiction and start to integrate it into your personality and sense of self.
But I think snapchat has face-altering features as in 3D modifications while photo booth only changed the image itself or maybe identified "head is at x,y" at most.
Snapchat can modify your head, make interactive animations and all that jazz. Do note that I never really used snapchat, but these are my impressions from the few times someone pointed it at me.