Vertical slashes: Vertical slashes are a set of moves that go along the Y-axis, basically from up to down, or from down to up. These are best used for direct attacks straight down the middle of the opponent, or to sever a limb or anything similar to that. Now, the vertical slash has more power than the horizontal one since the moves are easier to execute, and the user has more momentum. I believe one can strike hard enough to break a horizontal guard. The advantage over horizontal ones is power and execution. Regarding defensive capabilites, it can stop horizontal and diagonal, depending on the angle.
After doing the horizontal slash, Jiraya assumes a new stance where he moves his sword so it takes a vertical angle, with the tip pointing upwards. He doesn't wait too long before begining his offensive upon the dummy once more. He swings his arm upwards, and as it comes back down with the momentum, wood collides with wood and a loud echoing sound emits as the bokken and dummy collide. Even though the stroke was powerful it was not enough to break the dummy, but rather dent it.