Porting does one thing for sure. It ruins the collector value of the gun, if any exists. A secondary thing is to lower the resale value. From the standpoint of shooting it you make it a 1.) excellent sourse of light at night and 2.) a great cigar lighter 2 foot in front of the muzzle and 3.) louder than ears can stand on the street ( assuming you use ear protection on the range.)

My experience using handguns and rifles that have been ported or had muzzle brakes installed (same basic idea) is that if you feel you need porting to be able to control the recoil then what you really need is a lower caliber weapon. Weighted and ported guns in IPSC aside. In IPSC the times to shoot are so small and the money on the line so large that a port might give you a microsecond advantage in competition and decide a match with a lot at stake.