I'll get both, but I have a feeling that Xenoblade vs Last Story will be about the equivalent of Lufia 1 vs Final Fantasy 6, or Breath of Fire 1 vs Chrono Trigger. I expect The Last Story to be a MUCH more rewarding experience.
Of course, for me the big one will be Dragon Quest 10, which I very much expect to be my alltime favourite Wii game; in a similar way to how DQ 4, 5, and 9 are my favourite DS games (and this after I didn't think anything would surpass Phoenix Wright for me), and DQ8 is my favourite PS2 game (just ahead of Xenosaga Episode III).
I describe myself as a little dose of toxic masculinity.