I can only relate my experience with factory fitted pads.
Both my CZ550s (375 and 458) have deep, soft pads. They appear to work well, but the rifles are heavy anyway. The top tip of the pads are becoming damaged from placing the rifles in rifle rack (standing up) - too soft maybe?
The standard pad on my Merkel 500NE is very thin and relatively hard but works very well. My shoulder does not suffer at all from bruising or otherwise that might be related to a bad pad. The top of this pad has a hard plastic tip that prevents damage to the rubber pad when the rifle is racked. This tip sits above my shoulder and doesn't contact me during recoil - could likely cause bruising if it did.
