ST's have 100% steel one piece ferrules. Muzzy's have two peice aluminum ferrules.

ST's have .035" stainless steel blades. Muzzy MX-4's are .025" and regular Muzzy's are .020" thick.

Also, the ST's seem to fly better - exactly like field points. Possibly because the blades are at a steeper angle.

The ST's are basically a more sturdy design and more durable than the Muzzys. But Muzzy's are a great head also.