I would recommend quarter-sawn white oak. No question white oak is more durable than the more common red oak, and being quartersawn, it will be far less likely to warp or cup. Many boat builders would make their bulkheads/transoms, etc out of white oak because it was so stout. Ash is also a good choice and can have interesting grain/color. At our mill, ash is less $ than Oak (red or white). Quartersawn material will look pretty unique as the grain all runs parallel to the long dimension of the lumber. Too uniform for some, but really more stable.
