Re: brakes
The benefit would be reduced or practically eliminated muzzle jump and recoil. It's worth depends on your intended use. Competition shooters love efficient brakes to help with quick shooting. When target shooting with an efficient brake, you can spot your hits through the scope because of the reduced muzzle jump.
The one con is, the more efficient the brake is, the louder it tends to be. Not so bad for the one shooting as long as you have good ear pro, but it's pretty bad for bystanders.