It has always been our standard to use real plywood instead of OSB in our building. I have heard opposition from people who use OSB because, from what I hear, it may be easier to work with. Who knows.. my framing experience pretty much ended with a telephone book holder I made back in 8th grade woodshop class.
Now, we are not claiming to be experts in regard to plywood vs OSB. The owner let's just call him "my dad" framed with it back when he started and the believes it is a better product. Well, last week he found 2 pieces of 1/4" sheets of wood in the scrap pile out back. It just so happens that one happened to be plywood and the other OSB. Both sheets had been left out in the rain, sun, and snow of last year. I thought would just share with you what the same thickness of wood looked like after a year uncovered outdoors.
I believe the plywood held up a lot better than the OSB.