As Leach mentioned, the formations and motions are the most obvious difference. If the plays themselves are basically the same (and they are), how they get into them can be different. Leach famously uses really three main formations, with a few others sprinkled in for effect. A spread formation with two receivers to each side, another with three to one side and a single receiver to the other, and a two-back shotgun formation with three receivers. This does two things. One, all the players spend a maximum amount of time running the same route from the same spot. As the Airraid guys famously explained, their theory is that you cut a guy’s reps in practice in half if he has to practice a route from opposite sides of the field, and the quarterback has to learn to throw it to him on both sides. Instead, he can just master that curl route from the left side, every time. (The Indianapolis Colts have subscribed to this same theory with the uber-detailed Peyton Manning.)
The other thing the vanilla formations do is simplify things for the quarterback so he can check plays at the line. If you motion guys you might gain advantages, but you also muddy the reads for the quarterback. Leach’s preference is to have his players get to the line and let the quarterback find the right play.
