It all boils down to this = It all depends on this.

A person will say this expression before making a simple statement about a more complex matter. The statement should be a deciding factor between various possibilities. "Will I take you to jail tonight? Never mind that you are driving with your lights off at night - or that you ran two red lights- or that you almost ran over someone... It all boils down to if you pass my breathalyzer test."(this is a machine that can test alcohol level of a persons blood.) "If you get .07 you are free to go. At .08 you are coming with me."

it all boils down to this =to be reduced to its essentials. Example: It boils down to the question of who is going to win the game today.