I'm going to choose my best friend over him
Why do you want to choose your friend over him? Are you sure about this decision?
My friend has been with me going through relationships and always there for me.
Good friends are hard to find.  It is understandable to choose a best friend over a guy you are just dating.
I'm going to dump him.
It is a shame things did not work out but I am glad you are nurturing your friendship.