One of the most important aspects of your bo's performance will be the finish. The finish is basically how the wood feels when you slide your hands along the surface. A finish that fits your style will allow you to manipulate the weapon with ease, while an unsatisfactory finish will leave you frustrated.
The funny thing about finish is that it boils down to a matter of taste. There are right and wrong ways to go about it, but in the end you'll find yourself gravitating toward one style or another. Let's examine now the differences between stained and naturally finished wood.
A stained bo will have a very glossy and often attractive sheen to it. To the touch it feels smooth, glassy, and non-porous. Many people like a stained finished for it's consistency and for it's ability to help protect the wood against sweat, blood, and anything else that comes along.
Some bo come stained not unlike flooring, while others are oiled. Two of the best choices for oiling a bo include pre-bioled linseed oil and tung oil.
One problem with stained bos, especially ones that are stained with inappropriate paints and finishes, is that they can cause the hands to stick and skid as you try to slide across them. The sweat from the hand is not absorbed into the finish and therefore makes handling the weapon more difficult.
Natural finish on a bo basically means that the wood is sanded down to maximum smoothness but not coated in anything (or very lightly coated in an unobtrusive oil). Natural finish demonstrates the color and texture of the wood without being hidden or altered in any significant way.
One great thing about an unfinished bo is that it interacts with the hands better than a stained bo. It will absorb sweat and keep the hands in prime condition for sliding and manipulating the weapon, not to mention there is less of a skidding sensation along the surface.
The only major problem with the natural finish is susceptibility to outside moisture, and a higher likelihood of the grain opening and closing as the bo is exposed to different temperatures and moisture conditions. This makes routine maintenance more importance and reduces the possible longevity of the weapon.
Ultimately it's up to you to decide which sounds more appealing. Assess your physical attributes (for example, are you a big hand sweater?) and try out a few different styles to find the one perfect for you.