First of all, octagonal sticks are used in Okinawan Nunchaku & Bo. The reason is to cut your opponent w/ the edges. Sai also come in octagonal but they're not considered a "stick". Never saw an octagonal Tonfa - round, half-round & square only.
Baston (escrima/arnis/kali) should feel comfortable in your fist - not too large or small diameter & as long as the length of your relaxed arm from a cupped hand to your arm-pit.
Rattan is best because it's fiberous make-up absorbs the vibration of impact w/ other sticks & it's flexability promotes long life. This helps if you train for long periods. If your purpose is to hit people/animals, a hard wood will work fine. Don't worry about ratan not being hard enough; I've been hit too many times & can testify to its effecess.
As far as I know, bamboo is not advised because it splinters. Bamboo is hollow while ratan is solid. Ratan is a tree "vine" while bamboo is a member of the "grass" family. Select one w/ 3 "nodes" (the connection points between sections) because they're stronger than 2. Sometimes sticks will have phony nodes - burn rings where there are no nodes. 4 nodes are even better & more expensive.
Baston will have either a natural or laquered finish. Natural will be less slippery when hands get sweaty; laquered will protect the stick & last longer. Your preference, your call. Don't be swayed by fancy engraving (dragons), taped ends or swirley burn patterns.
Finally, although I've never used acrylic, I suspect that after much heavy usage, they could shatter! Maybe if you want to look cool in a demo or open tournament weapons forms...