I have both and love them both....you definitely feel the difference between the two....the ported barrel does not rise like the non-ported. If you are behind it you shouldn't notice the noise difference, but you will definitely notice if you are next to it! You can't appreciate what the porting does for you till you fire the two types of rifles back to back. It'll come down to where you shoot and personal preference though.
I have both ported and non ported guide guns, I agree with mazer, If you are are anywhere except behind it then it is loud for sure. The ported versions do reduce muzzle rise quite a bit which is nice for follow up shots. Doesn't do much for recoil though. That bieng said I prefer the ported version.
I have a ported 45-70 guide gun, an unported 22" 1895 and an unported 450 guide gun. Honestly, I can't tell the difference in any of the three in terms of recoil, or noise. The 45/70 guide is incredibly accurate, but that has nothing to do with the ports. I do think the ports LOOK cool.
C.G., I'll bet the 22" will chronograph the highest with factory ammo. Shorter barrels and ported barrels don't let the 45-70 burn all the powder before the bullet is gone. I love to look at a ported 45-70 being fired at night!
I have both and have trouble remembering what the report is on either. I only shoot with serious hearing protection in my all day range sessions and when hunting I only shoot once and it's totally instinctual and focused on the animal not the rifle. On rare occasions a finishing shot is necessary for humane reasons on walking up to a downed animal and thats the only time I ever notice recoil or noise but I can't say my ported is louder than non-ported. A rifle's report is loud and should only be fired at most twice without hearing protection. Hearing is important to any hunter. protect it when shooting for fun.
good hunting and hearing
I prefer the non ported version. Personally I cant tell any difference in muzzle rise but I can tell the difference in noise. As posted earlier, shoot in a deep ravine, or next to a big rock. The ported barrels will be excessivly loud. At least that has been my experience with a ported 30-06 I have.
I hunted with a guide in Africa that wouldn't allow ported guns because he is close to the shooter when shots are fired, especially when backing up hunters on dangerous game. But that was for his own needs.
The ported rifles are a bit louder, but accuracy is the same in both. I have heard that the reason the porting was discontinued was because the ports would fill with lead, I didn't have that problem with mine in all the time I owned it.
I think the extra holes added time to the rifle without the extra dollars at the time of sale. If you have a ported one, shoot it a and enjoy them as they should be.