I was looking at the sets at my local store and checked out the grain. Mapex was the only drum with horizontal grain on the inside and out. The Sonor 3003 and Yamahas had vertical interior grain. One of those sets has vertical outside and in, but I can't remember which one. Maybe Yamaha. My Premiers have horizontal in and out.
I think more mid range and upper end sets use some vertical grain than the Jalapeno site lets on. Exterior, it's only about appearance, interior...Nudrum raises an interesting point. There could be some difference in tone or volume.
Sonor points out on their site that when they sent manufacturing for certain models from Germany to Taiwan, they went from vertical to horizontal. It's about cost. Vertical is more expensive to machine bearing edges.
It seems to me that stacking plies in more than one direction is essential for dimensional stability, but I don't know if the direction of the inner ply would have as much impact as things like the type of wood or the inner finnish.
