Nothing is superior to Omnilock, just like no power is superior to OP. Omnilock can ignore every single law of reality, including logic, and do pretty much anything without the slightest form of effort. CO users may be able to do that as well, since they have Pataphysics Manipulation, but that only applies if the user can use that to the max.
In another way of saying it, every user of Omnilock is naturally Omnipotent, while only some users of CO are.
I'VE GOT THE ANSWER: User of Cosmic Otherness "exists" outside of everything. That makes such a user Nothingness itself (because Nothing exists outside of everything). However, Omnilock Users are "superior" because they "exist" outside of BOTH everything and Nothing.