Joffrey is an extremely spoilt and entitled little child, who just so happens to be King. We see time and again throughout the series how much of a brat he is, one who isnt really able to defend himself. Most of his worst deeds come in the form of threats (usually to Sansa), or are carried out by someone else (Ilyn Payne, The Hound). He does murder Ros with a crossbow, but that is the extent of blood on his hands. Ramsay, meanwhile, had a bastards upbringing, with none of the privileges that come with being heir to the Iron Throne. He had no knights to fight for him or dogs to do his bidding. All of the torture - both physical and mental - that he inflicts on his victims he does himself. If you stripped away Joffreys house and titles, and just had him living in Kings Landing, he wouldnt survive. If you took away Ramsays connection to Roose, and just had him somewhere in the North, hed probably still find a way of torturing and killing people.