[Dave at Pelican Parts]

The 205 will be a little easier to carry with you, and the overall diameter of both of your tire sizes is very close. If you're really concerned about space, you could go as narrow as 165/60-15, and that would only be a little shorter than either of your other tires. Though your tire busters may be unhappy about fitting a 165-width tire on a 6" wide rim...

--DD