Direction of plywood siding?

[EggWalrus]

If you are going for a finished look, I might also think about an overall plan for exterior decor, and use that process to locate a vertical strip over the plywood seam.

Like board and batten.

 

[aart]

Shingles on your roof have horizontal seams.

Not quite the same as overlapping sealing shingles.
Plywood sheathing would have butt joints.