Recently I took my wife's 4.25 M&P in 9MM and put in a threaded barrel and compensator for her. The recoil reduction is very noticeable compared to my standard 4.25" CORE. I'd really like to have some idea of how the non ported 4.25" gun compares to the 5" ported gun. Anyone ever done a side by side test? About what percentage of felt recoil would you estimate?
Thanks,
Chris.

it's a minor caliber to start with!

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"from my cold dead hands" C.H.

IIRC IDPA doesn't allow ported barrels.

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Improvise, Adapt, Overcome

So the Shield is not the gun in question. I'm not shooting IDPA either. Yeah it's just 9 MM, so recoil is not hardly brisk. But what I can tell is that the roughly 40% reduction in muzzle flip with the compensated 9 MM means I can shoot heck of a lot faster and more accurately, as can most people. I just don't want a barrel length of 5.5" if I can help it. This is a defensive gun, and I'm a pretty experienced shooter, having put around 100,000 rounds downrange in the last 12 years in practice, classes and competition. On a carry gun, I want EVERY advantage I can reasonably obtain. Sorry if I didn't articulate this in my original post. What I am getting is that you don't really know the answer however.

For a carry gun, the vast majority of defensive shooting instructors actually consider porting a disadvantage on a carry weapon, primarily due to it potentially adversely affecting compressed and retention shooting positions not to mention the resultant bullet velocity loss.

What is the verdict on muzzle flash in low light. Non-Ported vs Ported?

The difference between non-ported and ported is much less than the reduction from a real compensator. The ports halfway up a short 9mm barrel are more show than go.

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Science plus Art

I've gone through a bunch of experiments(actually about 3) with the following conclusions.
1. I had a 9mm 5" CORE Magna Ported, shooting minor PF ammo, I honestly didn't notice any appreciable difference between it and a non ported barrel.
2. I then built a Open division M&P 9, with frame mounted optic, KKM barrel, and I tried a couple of compensators. Again with minor PF ammo, it was actually worse because I had to spring it so light for function that the recoil was harsher. I did start to experiment with Major PF, it got better and better until I found the sweet spot at around 172 PF (124gr bullet at 1400 fps). I shot that for a couple of years but the strain was too much for the M&P slide, I ended up cracking 2 slides. S&W did replace one pistol (not just the slide) but wouldn't replace the one with the Magnaport cuts in the slide.
3. Gave up and went with a gun that was built for a compensator. Has worked flawless for the last 2 years.

What does this all mean in your case? Probably that there's no real simple answer to your question. Compensators and Ports need to be big enough, and have sufficient volume of gas to operate efficiently. I can't think of any store bought ammo that has enough gas to operate one. So, with enough playing around with springs, port shapes, and making your own custom ammo, you can probably get it to do what you want. Good luck

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Minimize the variables

I have both. The difference is negligible. Virtually no difference to me.

I have PC Shield 45 and yes, the porting does help with recoil and muzzle flip management. I also have a Glock 19C and that thing runs noticebly faster than a non-compensated Glock. I wouldn't own them if there wasn't a difference.

Porting is likely more preference than performance. To many it looks cool. While it may provide a slight performance improvement to some, I'm betting that equal or better gains could likely be achieved with good training and fundamentals. Just my personal opinion...

I own several ported pistols and enjoy shooting each and every one of them. I bought them for the looks, not as a means to gain performance improvements.

Compensator equipped barrels definitely make a big difference if the load makes enough gas.
Porting? I think it really depends on type & placement of ports, barrel length, load used, etc.
Not as much significance as a true comp, but I think some upward porting nearer the muzzle may help mitigate muzzle rise.
On the 4.25" M&P barrel the porting is small and at ~10 & 2 o'clock. I think it could make a minor difference other than being loud, but it would be fairly ammo dependent. Handloading could bring out more benefit.