I have an extra day after leaving Oktoberfest before heading down to Italy. If you had to pick one, which would you suggest?

PS Check out Fodors Friends on Facebook!

For one day Innsbruck, enough to savor that much smaller town and it's also a Hell a lot of more on the main route to Italy than the huge detour via Vienna

you'd be in Innsbruck in a few hours - several en route to Vienna, which probably could use more than one day to really see much of this rather huge city

Innsbruck because of geography and timing.
You could also consider going into the alto Adige section of Italy south of the Brenner Pass (Bolzano or Trento)

Forget Vienna. It is too far away. Save it for a separate trip and spend at least three days there.

I would recommend to drive down the A95 to Garmisch-Partenkirchen. You may drive westwards to Hohenschwangau/Neuschwanstein or eastwards to Kochelsee/Walchensee. From Garmisch, you have access to the Zugspitze.

Thanks everyone for taking a moment to offer your views and suggestions. I truly appreciate it!