link question

alright, i dont want any arguing or saying this is good, that setup sucks ass, just some ups and downs on both. i am look into a link but i wanna know what does a four link do that a three link doesnt? is a 3 link a good setup? do u need a panhard bar on a 3 link? i know on triangulated 4 links u dont correct? parrellel links push your axle to the side through the motion of ur suspension? just do the rundown on the setup if your willing.