Magna porting would reduce muzzle velocity a little, muzzle brake would not because the barrel is left intact. I'm not sure what the cost difference would be, magna port vs. have the barrel threaded for a brake.
Be sure to try a rifle that's ported or equipped with a brake first. The muzzle blast can be a bit much for some folks. I like my brakes but they took some getting used to, I have four now. I'm like a dog with his head out the window when I get hit with the blast. It's like surround sound vs. stereo for me. Adds to the experience.