I also prefer Magna-Porting and own three rifles so equipped. A brake will give a little better recoil reduction, no doubt, but the M-P is significantly quieter than the brake. Also, when shooting from prone, the brake kicks up a fearful dust storm; the M-P, lacking ventral vents, does not.
I usually ask a customer if they may ever use the rifle prone. If so, I just install a brake w/o holes in the bottom. Does the same job sans dust clouds.. Piece of cake.
If you hunt much from horseback and use a scabbard, you'll find a brake makes the gun really awkward to fish out, especially if the hunter must do so quickly.
Why? Just due to the extra length? The brakes I usually use are machined to the same diameter as the muzzle. Therefore, one is just going from a 24" to a 26" barrel or 26" to 28". Besides, most do not keep them on during a hunt - using them for benchwork/load development or similar but are removed when hunting..
Lastly, it comes down to aesthetics for me......a dreadful brake hanging off the end of your barrel ruins the clean lines of the rifle and makes it ugly as a mud fence.
I'll take that over the ugly holes in a nice barrel that can't be removed, anytime...
But whatever.. It's up to the individual owner.. As long as they intend to keep that rifle forever, doing a MP might not matter.. But if they ever want to sell it - be prepared for a potentially significant loss..