I got an MXR Supercomp, set a bit more for sustain and that way it is one of those pedals you donīt really notice are there, but notice when they are not. THe biggest effect I get is more sustain on my notes and a bit smoothing out in general.
What else it does I only notice when I really do a side by side with turning it on and off again. Then I notice how a few dynamics go away, in a good way, making the sound a tad more focused and my palm mutes sound and such sound fuller and again a bit more focused.
Try a side by side, see how palm mutes feel and if you get sustain differences.
Also check the settings, maybe you just donīt have the right ones.