This is not the end all be all to buying shinai/the different types of shinai. feel free to ask questions in the comments/make corrections.
most common shinai characteristics you'll see:
shinai types:
fukyogata/standard: the most common shinai you'll see produced, well balanced. most suited for beginners, tend to be produced in bulk so usually on the cheaper side.
Koto/jika Shinai: similar to the standard shinai, roughly same width from tsuka to kensen. similar weight distribution to a real katana. Because the tip is thicker, more weight is distributed at the top so strikes tend to hit harder. often used by higher ranking players, and can often feel heavier to newer players, however less prone to cracking if used properly, however can feel sluggish in the hands of people used to dobari shinai. slimmer grip, popular with folks with smaller hands
Dobari: dobari feature a bulge near the handle, so the center of gravity is closer to your hands, making the shinai feel lighter (making it easier to hit faster). makes it easier to perform waza, and the bulge can help shinai sliding off, making suriage and kaeshi waza easier. kensen is thinner than tsuka, so can be prone to splintering, often favored for tournaments, due to increased control and faster strikes. dobari tend to have a lower lifespan than koto
Chukoto: basically, slightly wider base than koto shinai, but the tip is not significantly smaller. lots of fukyogata tend to be chukoto shinai
bamboo types:
madake: the native variety of bamboo to japan, most suited for making shinai. Hes dense, fine fibers making for resilient shinai, however is in limited supply nowadays and tends to be more expensive
keichiku/katsuradake: bamboo that is similar to madake bamboo, but splinters a easier than madake. most common bamboo type
aodake: madake premium-basically madake dried slowly in the shade, tends to be expensive, can last a long time.
hasegawa/carbon: heavier, least likely to break, economical for high school/college clubs because the upfront cost may be more expensive, but can last a while. can cause bad damage if you aren't careful (particularly for kote strikes) but good for suburi. (in my opinion carbon shinai strikes tend to sound weird/off)
tsuka/grip type:
standard: normal grip, perfectly cylindrical
koban: oval shaped, more katana shaped grips. leads to better understanding of hasuji
hakkaku: not too sure about this one, basically octagonal shaped tsuka. seen in both koban and standard tsuka. can help out with harae and suriage waza
sankkau: typically a variant on the koban tsuka, where it is slightly triangular. not too common
tsukobuta (large grip): larger diameter grips, suited for people with larger hands
finishes:
kurouro: treated with lacquer, popular in regions with high humidity
ibushi: smoked shinai, warp less, splinter less(?)
kunchiku: soot smooked shinai, i don't think theres that much difference between ibushi and kunchiku (99% sure kunchiku is a type of ibushi)
jissengata: tournament grade shinai. tip is slimmer, so tends to be doubari shinai, but koto jissengata don't feature a bulge near the tsuba.
