The Standing Hip Abductor Exercise will improve your lateral strength (frontal plane) which will help develop your lateral power and speed . It is better to do this exercise on your feet since most athletic movements are done on your feet. Besides, the sit-down hip abductor machine doesn't work the hip muscles near enough.
Inadequate training of the gluteus medius (hips) will limit your athletic performance. Weakness in the gluteus medius can result in knee and back injuries. Weakness in the gluteus medius also contributes to instability when you walk, run and jump. In other words, you will avoid alot of injuries just by training the darn gluteus medius!