OSB is cheap, which is why builders use it. OSB is OK as sheathing, but as roof decking it has a tendency to 'telegraph' through shingles in this heat along the Gulf Coast.
I much prefer CDX, in any case. I always spec 1/2" CDX with a radiant barrier and taped joints for sheathing, and 1/2" CDX Tech-Shield for roof decking. For plywood subflooring I generally spec 1 1/8" CDX T&G.
YMMV