I've had an opportunity to own several revolvers which have been ported.
The first was a Ruger Super Blackhawk, 7.5" barrel, that I tried out for Metallic Silhouette. It was effective at reducing muzzle jump, but late in the day, flash was awful.
The second is a Model 29-4, 5"barrel, DX. The value of the Magnaporting is marginal at best. I've tried different stocks, loads, etc., and if there's any value in the porting, it's escaped me. The flash far outweighs any benefits.
I owned a Model 29-2, 4"; and I still own a second Model 29-2, 4". They've been tested by a couple of my friends in true blind-folded tests. None of us could tell any difference in muzzle flip. The noise level was higher; all of us had "doubled up", and the observers could said they could tell, although they knew when the ported revolver went off; so, those observations are a bit suspect. I sold the Magnaported model, and actually got more for it since it was ported.
I also own two 4" Model 19's, and the opinion was the same as the Model 29's; no difference in muzzle flip.
I owned a T/C Contender in .44Mag, Super 14 barrel. I could tell a difference from before and after having the barrel Magnaported. However, the T/C grip were not very comfortable. I tried Pachs, Herrett's, and a couple of different factory types. The pistol just isn't comfortable for a day at the range. Sold it about 6" months after the porting was done.
From my experience, unless the barrel length is at least 6" for a revolver, it makes absolutely no sense to have a ported revolver, unless you like muzzle flash at twilight.