I would say I have guts.
Having balls just seems like having the ability to face up to things you know will have a bad outcome. Balls is required for things like woeing girls at bars or talking back to your wife/gf, and driving a big truck.
When I think of guts, I think of courage, fortitude, and awesomeness. People with guts jump out of airplanes and climb mountains in blizzards.
Don't know if that makes sense but my 2 cents.