I put about 200 hours into Xenoblade and plan on going back. I am at 60 hours with Octopath, and will probably do a second playthrough (because I messed my party up a bit with the use of the nuts that increase different attributes).
Octopath's main problem is a lack of scope and epicness in its stories. As far as I can tell all 8 stories are unconnected, and end quickly after four chapters that each last about an hour. Also, as far as I can tell, Octopath really lacks any endgame bosses that let you take your level 3 classes and truly test their might. I beat all the endgame bosses with just my party at level 50. Once you get the secret level 3 classes, every boss in the game is a joke. Octopath has a great combat system, and fairly good pacing, but random battles occur a little too often for my tastes. In Bravely Default you could turn off random battles when moving through areas of the game to avoid fighting enemies that were too low of a level to bother with. Octopath doesn't really have this, so when you're moving through an area, which you've already mastered you are made to fight enemies that pose no threat to you. Some of the sidequests in Octopath are really obscure and confusing. A quest giver might mention in passing that they have a long lost mother, and its your job to go through the scores of towns trying to find said mother, and then bring them back to the quest giver. This sort of "I don't know what I"m supposed to do, until I randomly stumble upon it" quest structure is a bit annoying. Don't get me wrong, Octopath is a great game, and I'll list the good things about it when I write a review on it, but for now, I'm just listing the things that got on my nerves.
Xenoblade on the other hand has a much longer, much more epic story. The combat system is just as good as Octopath's if not better, and there's tons of late game bosses to test your party's skills to the limit. You can just avoid enemies that you don't want to fight in Xenoblade by running away from them. Sidequests are fun and rewarding because many of them often give you a whole new blade (character, not weapon) or something else useful. There's a sidequest marker that gives you a general idea of where to go next. The voice acting is fine if you're british, or if you just turn on Japanese voice acting (but don't know the langauge enough to cringe at it). Xenoblade is also, much much longer than Octopath. Like three times longer.