XCX has a bigger, more detailed world, than any other game out there. In some ways it is a lot better than the first game. Most of the flaws in XCX come from the game being too big. There are too many things to do, too many systems, and too many ways to build a character. It is very easy to get lost in XCX, in more ways than one. When building a character you can get lost and not know what to spend points in. When doing quests you can get buried in a seemingly unending stream of quests (This is especially true if you spend too much time doing story missions and ignoring sidequests.). When making augments, learning the nav system, and upgrading gear you can get lost. Xenoblade lacks a tutorial, and everything must be learned by reading the massive manual. There's too many options for your gear.
Anyway, if you want a game that will keep you busy for months, then get it. Splatoon is another game that will take up months of your time. At the very least rent those two games, before you sell your Wii U.