Are they even comparable? Or are their magecraft just different?

I feel like power levels in fate mostly depend on conceptual advantages rather than power.

In my opinion, yep, it's mostly about concept. That's how they defeated God Arjuna, that's also how they defeated Greek Gods in LB 5.

Yeah, one of the coolest things is seeing two figures from different stories fighting. But the Fate power system rarely really allows simple direct “vs” fights. What I mean is usually there are outside factors. Like how capable a master is, or how much magical energy is available. Or conceptual advantages or disadvantages.

Im not really complaining. Conceptual advantages allows generally weaker people to do pretty awesome things. We get things like Napoleon shooting ***** with a giant cannon, or Drake fighting ******** and stealing their *****. Which is such a cool feat.

Theoretically quite strong given that she is also sort of the basis for enchantress/witch types of characters.

However, Morgan is sort of the more well-known version of an enchantress in the modern times, while Circe has a much smaller role in the Illyad, amongst other Greek literature.

That is actually important, at least as far as I gathered from the original lore. The more well known they are, the more power they have when summoned. Not sure if it is as true in FGO's system though.

It's probably also why Louhi is stronger as well, given she is sort of more the basis for the modern witch. Just, loli-fied.

Yeah that makes sense. Fame is kinda hard to gauge. Especially for characters like Morgan. For as important as she is in Arthurian myth. Im pretty sure her actual story changes quite a bit in different iterations of the myth. That said I’ve never actually read it myself so I could be wrong.