Scyther has the ability technician to power up weaker moves. Aerial ace has a power of 90 not including STAb, and infinite accuracy can be nice. He has higher speed than scizor, but still has swords dance for the nice power. Technician is the main reason people pick scyther over scizor sometimes. His type coverage is also different. Scyther has ground immunity and more type coverage with flying than steel.