GUTS - is arriving home late after a night out with the guys, 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 guys, smelling of perfume and beer, lipstick on your collar, slapping your wife on the butt and having the balls to say: 'You're next.'
I hope this clears up any confusion on the definitions.
Medically speaking, there is no difference in the outcome, since both ultimately result in death.
Learn something new everyday eh???