Yapping session!
Xerxes has the abilities of the stones he's collected across his journey, meaning he has the powers of creation, destruction, soul manipulation, material manipulation, and I think something else but I forgot (remind me of what that is so I can discuss that too)
Edgyhead has the powers the Reality Ruby grants him, giving him the power to bend reality, precognition, the ability to create illusions, and mind reading.
Xerxes has the advantage when it comes to versatility, having more powers at his disposal. He also takes the strength and speed categories, being physically superior in these aspects.
Edgyhead has the advantage when it comes to intelligence and experience, with millions of years of fighting and learning on his hypothetical-belt. And while Xerxes does have the versatility advantage, it can be argued that Edgyhead has some better powers.
Xerxes' counters to Edgyhead:
Can mix creation and destruction to replicate reality shifting
Can disrupt illusions
Can overwhelm him physically
Edgyhead's counters to Xerxes:
Can avoid his powers with precognition
Can resist soul bending with his corrupted and beaten mind
Already has knowledge of what Xerxes has done
My opinion?
I say Xerxes wins 40% of the time, Edgyhead wins 60% of the time. Edgyhead's abilities like precognition combined with his experience and intelligence would give him an advantage, but Xerxes still has the capability to beat him, with his physical superiority and more diverse skill set, although I find is slightly more unlikely than the prior.
don't scream at me.