Based on what I've seen so far, I'd say Xenoblade Chronicles X. The other game is a crossover, and if it doesn't fit into the canon of either franchise it's drawing from, it could just as easily turn off their loyal but niche fanbases.
From what I can tell, SMT and Fire Emblem and both sub-million selling franchises (with a few exceptions), and I don't see the crossover pushing as much as the highest entries in the respective series. It's not quite as simple as assuming the game will sell as much as the combined total of both games, as I'm sure there's a fair bit of overlap. Meanwhile X seems to be getting a decent amount of promotion from Nintendo, and is a known sequel to a very highly rated game. I'd be surprised if it sold under a million LTD. Only time will tell though, I could easily be wrong.
NNID: Zephyr25 / PSN: Zephyr--25 / Switch: SW-4450-3680-7334
