They change the direction of the sound, not the total DB. From the shooter's position they're definitely louder so that's all that matters. I use them on some of my prairie dog rifles because they allow you to spot your shots through the scope at 20+ power. I'm always doubled up on hearing protection and after a day of shooting 2-300 rounds you'll start to feel even a 22-250 on the shoulder, the brakes make a long day of shooting a lot more pleasant.
Brakes have their place like everything else. If you shoot a lot you'll come to appreciate them. If you're a one box a year shooter who stuffs the wife's cotton balls in his ears for hearing protection you'll probably hate them. I only have them on a few rifles but they serve a purpose on those rifles and I wouldn't change them.
This. Crow Hunter has it right.
