Here’s the official distinction; straight from the British Medical Journal: Volume 323; page 295.
GUTS – Is arriving home late, after a night out with the lads, being met by your wife with a broom, and having the Guts to ask: “Are you still cleaning, or are you flying somewhere? ”
BALLS – Is coming home late after a night out with the lads, smelling of perfume and beer, lipstick on your collar, slapping your wife on the butt and having the Balls to say: “You’re next, Chubby”
I trust this clears up any confusion. Medically speaking, there is no difference in the outcome; both are fatal.