My p9 Ultra is a 40. It makes a HUGE difference. My wife basically took this gun from me because she did not like the sharp snappy recoil of the MD96 and preferred the push of the P9. It is louder yes, but that can be dealt with so she shot it a lot. First time she tried it without the ports her comment was the gun is broken.
You go from a snappy sharp rap in the web of the hand without the ports to a more gradual shove with the ports. Put some 135's that are book max reloads with the right powder (one of the slower ones like AA7) and you can get the barrel to recoil down. It is neat to be able to see the target after you fire the gun instead of having the gun obscure it.
I don't really have that many pictures to show the difference. Maybe I should pull the barrels and show you the results. Here are guns in question though.
As an aside, I have shot over 8,261 rounds down the P9 and changed the barrel out at round 5675. I will try and pull it apart and shoot some new pictures. I have not shot the gun in a long time (10/24/05) as I have gotten tired of chasing brass and now I shoot more revolvers and autoloaders.