When you shoot for real (in self defense, not at the range), many of the distracting features of gunfire are not noticed. In an adrenalin charged situation, many if not most people report things like auditory exclusion (reduced hearing, gun shots sound like small pops) and tachypsychia (time slows down). Muzzle flash is not likely to even be noticed by the shooter.
Good ammo like Ranger SXT and Speer Gold Dot HP's use triple based, low flash powders that do not have much flash signature at all. Gold Dot ammo has a slight glow at the muzzle at night.
Any other ammo (FMJ range ammo or handloads) are unsuitable for defense for practical or legal reasons and can have massive muzzle flash that may be blinding. My .41 Magnum handloads will make a blast about 18" out the cylinder gap and a good 2 feet out of the muzzle.