I'll pretty much echo what others have said about the characters, I'm not a fan of FFX's characters overall, and Xenogears has great characters.

For art direction, neither of them actually rank that high on my list, but Xenogears does have the edge because of its sci-fi aspects (and mechs, I love mechs)

Which leaves gameplay, where honestly they're pretty even for me. I really like aspects of the Xenogears combat (and the fact you can fight in mechs), but it's still an ATB system, and that part I'm not a fan of. FFX meanwhile has my vastly-preferred turn-based system but doesn't do much with it.

So that's a 2-0 and a draw (or 3-1) for Xenogears