Remember, the "rail system" or any other top of bench system, breaks up, cuts up, grooves up the bench top.
Not so with the underbench "receiver system" which leaves the bench top un-mared and allows for changing of loading tools for the job, even having a vice at the bench if desired, And/Or having as many tools up and ready as you have receivers.
Having a clean smooth and unbroken bench top and your tools in place for use, all at the same time is like having your cake and eating it too.
Keep em coming!
Crusty Deary Ol'Coot