Every so often people ask about the ported Glocks. As an owner of a Glock 19c, a ported 9mm compact, I can answer those question.
Q: Does the porting reduce recoil?
A: Yes, by a small amount.
Q: Will the porting make the firearm louder?
A: Yes, it is very noticeable firing indoors.
Q: Does the ported 9mm Glocks shoot jets of flame from the ports?
A: Only if you use really poor quality ammunition with no flash suppressant. Even then, the blast from the muzzle will far surpass the blast from the porting.
Q: Are there problems from shooting in a retention position with a ported Glock.
A: Not if you cant the pistol slightly away from you.
Q: Will carbon build up on the front of my front night sight?
A: Yes, but not enough to prevent its use.(Under normal firing conditions)
Q: Will the carbon buildup on the barrel and slide be hard to clean?
A: No harder or longer then cleaning a standard Glock.
Q: Is it worth getting a ported 9mm.
A: No, however other calibers might benefit more from porting.