We used Advantech subfloor from Huber Wood Engineering. It's supposed to resist weather damage during construction. Panels are warranted not to require sanding due to moisture absorption during installation, and they have a 50 year limited warranty. Our local building supply company says that Advantech subflooring has taken over the market -- they sell very little plywood subfloor anymore.
We're impressed. Advantech is flat and has the nailing pattern marked right on the panel. The tongue and grooves fit together easily. It's even easy to cut with a handsaw.