I enjoy all clean-as-can-be competitive style racing from shuffle, PP restricted races, and high power Viper/Vette/Enzo racing at Daytona.
What I don't like is dirty racing and racers that quit the race just because they aren't going to win that event. If someone has a run on you for a clean pass, so be it. Ramming into them to prevent the pass isn't going to make you any new friends. There is a lot more to racing than winning every race. I also try to finish every race that I enter regardless of position.