The only reason (advantage) to use a GE fare instead of OWE is to be able to fly on the additional airlines allowed on the GE. If all of your routes are available on Oneworld, then there is no reason or benefit in considering the GE product. But if you need to fly to certain places or routes, then only the GE will get you there. Otherwise you are always better off with OWE instead. Makes it an easy choice, if you know your routing or can give up on the GE sectors.