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I have a Mag-Na-Ported .375 H&H, and the difference is appreciable - the 'porting made it possible for me to fire a couple of boxes off a benchrest (for example, during load development) whereas before, the recoil after one box began to bother me.

I also have a reworked .357 revolver, which includes a compensator milled into the muzzle. There's a noticeable reduction in recoil and muzzle flip when shooting full power loads - particularly the 125 JHPs - but for .38s the difference is imperceptible. (And this compensator is not the most efficient design - the end is a bit more "open" than ideal, in order to enable the firing of Glaser Safety Slugs, which allegedly tend to expand a bit in diameter as they leave the muzzle.)

A lot of compensator efficiency depends on how much powder you're burning, which affects the pressure at the muzzle. Winchester's loading data recommends, IIRC, around 18 grains of their #296 powder for the 125 JHP . . . a .38 Special wadcutter will use 2.7 grains of Bullseye; less muzzle pressure due to lower volume of powder gas, so less effect from a compensator.

IIRC, old USGI Ball ammo in a .45 used around 4.6 grains of "Bullseye #2" which is a .45 barrel won't generate a lot of pressure. Many 9mm P loads will similarly use 5 grains or less powder, and since they're essentially the same diameter as a .357 (only a few thousandths smaller) a compensator won't be particularly effective on either.