Another route you could look into would be to see how much the 2x4 ply costs. See how much you are saving on full sheets.
Might be worthwhile to just get 2x4 sheets for all the aggravation of dealing with full sheets.
I would agree that as long as the shelves don't get wet and stay wet all the time regular ply or OSB should work fine and last a long time. Regular plywood is pretty resilient.
Just seems like you may be putting too much thought into this.
If you aren't set up to cut 4x8 sheets then go the easy route. Those 2x4 sheets of regular plywood are still probably a lot cheaper than some kind of specialty plywood.
Last edited by against_the_grain; 12-17-2012 at 07:33 PM.