Is this a good thing about my boyfriend?

So me and my boyfriend are on and off and sometimes i dump him sometimes he dumps me for various reasons but usualy when we do breakup for a long time i end up dating someone else and so does he, he dates this other girl and people say when ever he is dating her he is a jerk to everyone but when he is dating me he is nice to everyone is it good that he is nicer to people when he is dating me? cause i thought he was a jerk to ppl when he is dating her is maybe cause he is more confident when he is dating her? sorry for any misspellings or any typos ! (: