I have a 6" S&W 629-1; an Andy Cannon RSBH 7 1/2"; and a 4 5/8" Mag-Na-Port Custom Tomahawk RSBH; all are mag-na-ported.
I'm glad all three are, it sure doesn't negatively affect my shooting and it seems to help the felt recoil and muzzle jump.
Around here the process seems to be a bonus to purchasers, but maybe they're usually shooters not sophisticated collectors.