Jermome did a real good blog on this, but to summarize
OPEN with EAP = Authentication bit set to 0. All EAP methods but LEAP require this.
Network EAP = Authentication bit set to 1. LEAP requires this.
Some Cisco clients such as AP's require both when using a EAP method other than LEAP. This is for legacy reasons.
As only CCX devices can use LEAP, setting the method to Network EAP will allow only CCX devices to connect.