A new gameplay experience and enemy designs would definitely go to Xenoblade since its pretty much a new rpg compared to the decade returning Final Fantasy series.
Aside from that, FFXV would have more content, side quests, monsters, story, scale etc. Its almost an unfair comparison if you ask me. (though this is me basing my points from experience with FFXII, FFIX, FFVII, FFVIII, FFX, FFXIV compared to Wiis Xenoblade)







