There is a medical distinction between Guts and Balls.
We've heard colleagues referring to people with Guts, or with Balls.

Do they, however, know the difference between them?

Heres 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 bum and having the Balls to say: 'You're next, Chubby.'

I trust this clears up any confusion.

Medically speaking, there is no difference in outcome; both are fatal.