The Scorp has a lower Kv spec, but only by 120RPM, and a lower rated power output, but still plenty of power for the MX450- you have to fly the MX hard to use more than 400W. On the other hand, even at 250-300W (pretty spirited flying), the Ammo motor tends to run pretty hot, while the Scorp will stay comfortably warm on a 12-13T pinion. I personally think the Ammo is a very good fixed wing motor, but the Scorp is better for helis.