Depending on what you're talking about. Overall Bo Staff and Metal So staff are hardly different, yet, if you're good at evading and attacking or you want more attack speed, regular Bo Staff is your go to. Personally I say Bo Staff is the best because: The weapon is free, has more attack speed which allows for swifter kills and swings, albeit the damage is a little less but then again the attack speed makes up for it, and the glory I believe is slightly less longer than Metal Bo Staff; makes no difference though (as you can swap them out).
Overall even though there is hardly a difference, Bo Staff in my opinion is better than Metal Bo Staff. More damage doesn't always mean better.