I don't know anything, so this is speculation. The longer pipes should have a deeper exhaust note than the shortshots. The shortshots will sound louder to you since they're closer to your ear. The shortshots should weigh less.
Short Shots! Thats what pipes im getting next. There defently alot louder then long pipes. And i always want to be louder. Plus i think they look so much better. I like how they show off the rear wheel and dont take away from the look of the bike.