Muzzle brakes are also known as compensators. They are meant to slam into a fixed barrier. The muzzle brake seems to be so simple when it is being explained, but actually, this is a bit hard to do in the real world. The flash hider is something that you would need when you are using an AR Barrel.
This is used to make sure that there will be enough time to cool down and make the pressure manageable. This can also be used when the shooter would like to make sure that the flash is manageable. These two things are used differently, but they are meant to make guns work better whenever they are used.