Arwen or Éowyn ?

Depends on what Arwen’s soup tastes like

Speaking as a man ... clearly Arwen😉

Why would he fall for Éowyn? Aragorn has been in love with Arwen for decades by this point, whatever Éowyn's good qualities, she doesn't even tempt him because his heart is already taken. And as a more practical matter, Arwen is an Elf, and therefore ageless; and though she chooses to renounce her immortality for Aragorn in the end, forgoing any possibility of sailing to the Undying Lands to join her father and the rest of her kin, there's no indication anywhere in Tolkien's writings that she aged after making that choice, and Aragorn (being one of the long-lived Dúnedain) lived at least another hundred years after becoming King Elessar. (Not long after Aragorn's death in old age, Arwen quietly and peacefully laid down her own life and followed him -- his loss finally making her understand why and how the Númenóreans had been lured by Sauron into their fall.) Éowyn, on the other hand was already a thirty-ish mortal woman, who would have grown old and died while Aragorn still had many decades left to him.

Arwen was a better match for him in every way. And in the books (unlike the movies, which diminished Aragorn's character by making him a man who was running from his destiny and responsibility), Elrond had made claiming the kingship the condition for giving Aragorn his blessing to marry Arwen. Elrond knew that Arwen would follow Aragorn wherever Men went after they died, and not to the Undying Lands where the Elves went when they left the world. And he refused to allow her to be sundered from her people for any less cause than the restoration of the kingdoms of Gondor and Arnor.

Arwen has that slight Down’s Syndrome look so I’m leaning Eowyn.

IMHO the Eowyn of the films was a bit miscast. The Eowyn of the books is supposed to be this beautiful blonde who's tall and strong enough to pass as a young man, and in the films they cast a fragile little wisp of a woman who is pretty but not beautiful. It takes strength and heft to hold your own on a Medieval battlefield, a fragile little 90-pound wisp has less chance than that kid from "The Two Towers"!

Liv Tyler did as much with the role of Arwen as could be done, she looked right and acted ethereal, so she gets my vote.

Eowyn was probably the better lay, even if Arwen was prettier.

Going by the film, one thing's for sure, if I was Aragorn and had already been in love with Arwen for decades, the last thing I would have done is walked into Theoden's throne room in the middle of the night, saw beautiful Eowyn sleeping there on the sofa, and decide to stick around and see what happens... which is what he does. Why give Eowyn a false hope of love? Not worth the temptation and the repercussions afterwards, if I am in love with Arwen already.

Eowyn, Arwen sucks. She never should have had such a big part in the story, in the novel she appears in like 2 scenes and her entire dilemma is summarized in like 2 sentences.