Clearly Xenoblade Chronicles is better. To explain: not that XCX is a bad game, on the contrary. But XCX is a different game than XC, and many of the choices in XC I liked more.
pro XC: better story, better characters (even NPCs), better music, AND YOU PLAY ON FREAKING TITANS
pro XCX: even more exploration and exploration is really rewarding, Skells are great (really, I like them)