Xenoblade Chronicles X easily. It sold great considering it was a GameStop exclusive in the US. Also, the Wii's infamous casual crowd defiantly didn't buy the first, so the Wii U install base isn't much of a factor for X.

It's not really a contest. Xenoblade was widely regarded as the best rpg of last gen, and thus there is hype for it's "sequel". SMT and FE are both loved series, with ardent fanbases. But they're both also still relatively niche. Yes, the last FE for 3DS did better than any other entry before it, so perhaps it's slowly getting more popular. But X is still going to outsell SMT x FE.

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.

I know, fire emblem doesn't sell as well on console as it does on handheld so not sure if a crossover will do better than xenoblade

Xenoblade easily, the first game got near 1 million being a new IP.

Easily Xenoblade Chronicles X, because Fire Emblem and SMT mostly belong to handhelds nowadays!

Reading this, maybe the X (Cross) in Xenoblade Chronicles X also stands for Crossover. As the ending of Xenoblade 1 suggests, the next game is a crossover with the Xenosaga series.

Xenoblade Chronicles X because SMT X Fire Emblem is a little more niche than Xenoblade imo.

I think xenoblade chronicles X easily, but they both won't do very well.