How would u react if ur sister says that you would be better with ur ex?

I love my boyfriend and i'm kind of hurt my sister said this to me. My bf and I have our ups and downs because its a long distance relationship but he is a lot different from my ex. My boyfriend is very attentive, sweet and kind and has NEVER yelled at me. My ex was reallllly loving and affectionate but very very moody and i couldn't handle that. It makes me think, but then again an ex is an ex for a reason, right? How should i go about this...