Why don't you just compare them at their basic and Absoute level?
Psionics Vs Magic
Absolute Psionic Power vs Almighty Magic
The answer is Obvious now, I think.
Nobody says that about Psionic no matter what level its at.
Something I always wondered though, does Complete Arsenal include Omniscience and Omnipresence or are they in a different Category?
Well as its complete, Meta power Manipulation is part of the package so, just seal the ones that would make you feel like you don't have free will like Omnichronal Perception and use Power Level Manipulation to decrease the level of the rest so you can grow/evolve with them slowly. However don't be an idiot and seal away an important defense power. Make sure to keep Psychic Immunity, Absolute Invulnerability, Absolute Immortality, Erasure Immunity, Soul Anchoring and Power Anchoring etc... At least that is what I would do.
The power is not about being the only one who can use it, it is just that no one can copy, mimick or absorb anything of the users of singularity. For example imaging there are three people, Person A, B and C, now lets say both Person A and Person B have Fire Manipulation and on top of that Person B also have singularity and Person C have Power absorbtion, Power replication and Shapeshiting, now if S/he tries to user her/his power on Person A and B, Person C would only be successful on using her/his power on Person A.
Sorry if that was a very long way of explaining a simple thing.