Honestly, power potential wise both are relatively even.

Im actually writing a fan fic of this rn called War of the End Bringers

@Slyme quin sick i always wanted a story where these two fight is there a way to read it on here after you release it?

Both are pretty even, but one is a planetary threat who wants to be Celestial level cosmic and is a cosmic threat. Either way, this is a much need battle that Marvel needs to make happen.

I personally always felt that the reason Apocalypse seems lower level is just because his interests are primarily earth based.

I think if he set out for a more galactic goal he could achieve it with ease, much like thanos. Id love to see a plotline where he does

He could be a threat, like he has to the Inhumans and such but its his body. Every time he goes into stasis, he get stronger, and in time he needs a new body. We have seen him go full out, but that burns through the body even faster. Hell, during the end battle of X of Sword thing, he could have easily gone Sentential size or bigger and just blast the enemies to nothing. That's why he did the 12 thing, to take X-Man's body, which would have been strong enough. Or Cables in the future, but it turned out to be Stryfe.

X-Factor Vol 1 #68