If you were only using the the spare tire to throw at corners (or the 6-10, 9, etc.) then you would probably be fine with getting a Rebel Tank and flattening it out. If you used it shoot other, more complicated (relatively at least) stuff then the Arctic Sniper would be better since it reacts much more closely to the general plastic ball.
But feel plays a huge part in it and that's totally an individual case-by-case basis. Personally I still like using a plastic ball and the angles (close to none or slight) I can achieve with it better than flattening out a urethane or resin ball. Others I know are want the extra spot in their bag for another strike ball so they're fine with throwing whatever at spares. Like jkirkerx said, pure preference.