User blog comment:DirgeOfCerberus111/Adeptus Custodes Vs. Grey Knights/@comment-1536954-20110819090422

The Grey Knights chapter primarily serves with the Ordo Malleus, and are intended entirely for the destruction of daemons. Where as the Adeptus Custodes are intended for the defence of the Emperor and the Imperial Palace, and therefore would have to be adept for fighting Heretics, Chaos, daemons, aliens and anything that may threaten the Emperor. It is very likely that the Adeptus Custodes would probably win. It is mentioned on Lexicanum that "The Custodes are slightly larger and stronger than Space Marines"