If one gun really was better than the others the secret wouldn't last very long and you would never see anything else used.
If any quality PCP is running right and is well set up with suitable pellets then the groups will be identical. So much of what ends up being used is just a platform for modifications to the point that even barrels are changed.
Given the flaky nature of our minds we have to use a gun that we think is best. Truth is that care in rifle preparation, scope set up and pellet selection are more important than what brand or type of rifle and scope are used.