Pros and cons time. Some of which have already been covered and some not.
The reason for porting is to cut down on the perceived recoil and keep the muzzle down more shot for shot.Less rise as it were. It is recommended by the companies that do this that porting be done for cartridges of high intensity. The physics that go into this are the reason with out going into all the jargon. The higher the intensity the cartridge, usually the better the porting works.
Much research and experimentation have been done by the companies on this. Every variable and cartridge considered. This goes for brew your own wildcat rounds as well.
38 Specials and 9mm. cartridges are not usually considered in the high intensity class. Some 9mm loads are close or are at that. +P+ come to mind, but not the majority of these. Results are that with low or middle intensity loads the porting does not do it's job as well as for the more powerful ones.Efficiency is degraded all the way around and makes little or no difference in what the porting is does or is supposed to accomplish.
Hot gasses coming out the vents can cause major problems as well. The increased muzzle blast has disoriented people inside dwellings and under low light conditions. The shock wave coming out up, and directly back does this. Being out of commission for a short period of time can prove fatal.
Night vision can be dazzled or knocked out for precious time in a fight. You just lit yourself up. Maybe not much, but enough. Eye sight has to readjust and get back to normal in low light or no light, giving the attacker the advantage for a short period of time.
If the attacker gets close in and is at body contact range, to keep the gun away, the person has to tuck the gun in close to the body. Blowtorch hot gasses are now near your body and face. Especially coming up at the face and eyes at very close range.
Major injury or a dibilitating wounds can result that can cost one their life.
If the bad guy grabs a hold of the gun by the muzzle and the trigger is pulled, then he gets the whole nasty blowtorch effect done to his hand. That's the upside of the down one.
Gun writers,testers,and shooters have reported little difference in mild or low intensity cartridge recoil reduction with porting. Same for muzzle rise. So the physics say there is not going to be that much redirect of the forces causing the problems you are facing.
Pros: There is less of the forces to deal with. There will be some small gains in less muzzle jump and felt recoil.
I have a relative who has some arthritis and carpal tunnel syndrome. The doc told him shooting was over for his life. Then he went and purchased Ruger SP101s,two of them, both in .32H&R magnum. There are mild .32 cartridges that can be used in those revolvers, and if needed, the higher level of .32 magnum power can be utilized.
While these are not the top picks for defense there are many things the .32 caliber cartridges can still do. Much better than the alternative. The doc put the relative back on the shooting wagon because of the change to the lower powered cartridges.
It doesn't hurt that the guy reloads as well. He can tailor the ammo better to his specs and needs.
Ma-na-port does a good job with the porting and are the standard by which others are judged. There are a couple others, but they escape me for the moment. Staff and members may be of help at this point.
For defensive purposes, porting has many things to be considered. On a hunting gun this makes more sense. For longer barreled guns it makes sense to a point. For defense? That's a call the owner has to make and be the judge of.
Porting pistols means there could reliability troubles. The gas going out the port may be energy needed to work the action and what's needed is going out the port.
Reputable porting companies may or may not be able to get fit and function to work for certain specified brands,makes, and models. It can be done to some pistols There are limitations as to what ones it can be done to.