I'd opt for a flash suppressor if I could legally get away with it. Easier to clean and looks much better. Since I'm in CA, it's the brake for my M1A.
As for the brake being louder and more obnoxious vs the flash suppressor, I sure as heck can't tell and neither can my brother, father, coworkers, and last but not least, 5'2" asian girlfriend.
Louder? We couldn't tell.
Muzzle blast? We couldn't tell.
Recoil? We couldn't tell.
Blind fold us up and put us behind the wheel of my brother's M1A (flash suppressor) and my own (CA brake) and we won't be able to differentiate between the two. Well, that's not entirely true. His trigger's a bit better than mine...
My experiences and those of my family, coworkers and girlfriend do not reflect those of others. Your mileage MAY vary.
Jim