I recently reread Till We Have Faces: A Myth Retold by C. S. Lewis so I thought it would be a good time to start this topic.

I've read Lewis fans opine that they imagine a story about the adult Susan coming back to Narnia would be like Orual's story in TWHF. I doubt this since to me, Susan and Orual seem like opposites. Even their similarities emphasize their differences. (Major Spoilers Ahead!)

For example, both Susan and Orual become great queens, but TWHF shows that this doesn't necessarily make her a good person whereas in the Narnia books a good ruler always equals a generally good person. TWHF also shows that some of Orual's good actions as queen, such as freeing some of her slaves, also benefit her personally and that she owes a lot to her advisers. It's a more complex, adult look at politics than we see in Narnia. (I don't mean that to criticize Narnia BTW! It's not trying to give any complex, adult look at politics.) 

Both queens have a maternal streak despite never marrying. Orual serves as a mother to her half-sister, Psyche, and Edmund accuses Susan of "trying to talk like Mother" at the beginning of LWW and it's implied she serves as a mother figure to Corin in HHB. But while Orual's motherly relationship with Psyche starts out well (though there's foreshadowing early on that it's unhealthily possessive and obsessive) but she ends up being abusive to her. Susan, on the other, seems like a good mother figure. (I imagine she was a better mother to Corin than she was to her siblings but that's because she was older then.) 

When Orual becomes queen, she excels at taking on a traditionally masculine role. (In her misogynistic culture, there was probably no other way she could rule.) Susan, on the other hand, "is more like an ordinary grown-up lady." In The Last Battle, we're told that Susan is "interested in nothing except nylons and lipstick and invitations." But Orual, who has a lot of what the kids these days call internalized misogyny, looks down on women who are interested in her culture's equivalent of "nylons and lipstick." As for invitations, she really doesn't enjoy the only official feast she attends as queen.

We're also told that Susan is "no good at schoolwork (though otherwise very old for her age.") Orual, on the other hand, is a good student which is part of what enables her to become a great queen despite the odds stacked against her. Another thing Orual has that Susan hasn't is stamina. Susan is the Pevensie most likely to complain or worry about danger. I can't say Orual doesn't complain since the entire book she narrates begins as a "complaint against the gods" but she's a lot more physically tough. 

The flipside of that is that Susan has a lot of compassion even on her rivals whereas Orual, partly because of the cruel world in which she grows up, can be ruthless. I feel like if Rabadash made a move on Orual, she'd...well, at first, she'd probably be flattered because someone was attracted to her for once but then she'd cut off his head.  

The most obvious difference is that Susan is the beauty of her family both in Narnia and in England whereas Orual has a face that could stop a clock. If anything, Lucy is more of a parallel to Orual in VDT: outwardly loving towards her prettier sister but envious and resentful deep down.

On reflection though, I do think there's a parallel to be drawn between Susan and Orual, just not with the Susan in The Last Battle. In Prince Caspian, it's implied that Susan initially can't see Aslan because it would be more convenient for her if he wasn't really there. In Till We Have Faces, Orual can't see Psyche's palace because (on a more subconscious level than Susan) she doesn't want it to exist. 

I still think Orual and Susan would hate each other if they met. But then again, a big theme in TWHF is that the people Orual hates the most are those with whom she has much in common.