Kevin Hart is first of all a cleaner stand up comedian. He doesn't cuss as much as Katt Williams. Also Kevin Hart is out there more. Think about Ride Along, Think Like a Man 1 and 2, and it is said that there is to be a Ride Along 2 also he has Real Husbands of Hollywood. Katt Williams on the other hand isn't really out there in movies, or tv shows, or even in his stand up.