My position is that depending on the type of work you will be doing, you may need an xjet AND an extension pole.
For me, I could not function without either. They both have there purposes. For example, try washing brick 10 feet up without an extension pole, the xjet is not gonna do squat for you.
While I agree 100% that the service for ExtendaWand is not what it should be, I also have to say they are a heck of a lot better than the cheap fiberglass twist-cam pieces of crap.
I have not used a Coress so I can't comment whether they are the best.