Why worry about a weapon's quality?
So that when you are practicing kentaijo your nifty new bokken doesn't shatter when it is knocked aside by your partner's hickory jo, thereby endangering everyone in the dojo with the sharp flying splinters. Yeah someone with good ki can concievably extend it into a pvc pipe making it unbreakable. But I can't and doubt I will be able to for a good many years so I train with the highest quality weapons I can get my hands on.
Aikikid, Kingfisher has an article on their website about different woods for bokken and jo. That would be a good place to start.