There are no two ways about it; Sodapop loves fighting. Whenever there's a major rumble going down, you can be sure that he'll be right there in the thick of things, fists flying and arms flailing.
As Ponyboy observes, Soda, like Steve, gets into fights because he has way too much energy. Like a lot of young men his age, Soda has bags of energy to burn, and he feels fighting is one of the best ways for him to do this.
Soda blithely describes fighting as if it were just another leisure activity that people do in their spare time. Amazingly, he likens it to a sporting contest such as dancing or drag racing. Contrast this with Steve's attitude: he openly admits that he wants to stomp on Socs' heads and give them a good beating. Whereas Soda enjoys the excitement of fighting, Steve enjoys inflicting pain.
Because Soda's motivated to fight by an excess of energy rather than from hate, Ponyboy's pretty certain that he would stop fighting if someone got seriously injured or killed. The same could not be said of Steve. As he's motivated to fight by hatred, it's almost certain that he'd keep on hating and fighting no matter what happened.