Solid oak is the classic choice if you want a table that can outlast rain and a few inspectors, but it’s pricey and will still need a good seal to keep from warping. Engineered wood is cheaper, less prone to movement, and you can get a nice finish, but you’ll have to watch the seams and make sure the finish is robust. Either way, the joinery will win out over the material itself, so make the joints solid and the finish tight.