Vuurwapen did an interesting comparison of muzzle brake/flash hider/compensator in two parts.
In Part 1, muzzle flash is covered. You can slide through each photo for more photos.
http://vuurwapenblog.com/2013/10/03/ar15-muzzle-brakeflash-hidercompensator-comparison-part-1/
In Part 2, sound level is covered.
http://vuurwapenblog.com/2013/10/05/ar15-muzzle-brakeflash-hidercompensator-comparison-part-2/
From: Vuurwapen blog