Elk and stag are much more similar to each other. Elk and buffalo (or stag and ram horn) aren't similar at all. I think a lot of folks who like stag will also like elk. Splitting them now rather than later may not result in a very representative result. I think buffalo and ram would not get many votes if they were grouped together.
Also, grouping all the woods together would probably give wood a better shot at winning. Splitting the woods up may not give them much of a chance to get a majority vote.
In my opinion....any of these could be good... in no particular order... Delrin, diamondwood, real wood, elk, stag, carbon fiber, micarta.
It really depends on the difference in price. Also, stag and elk are favorites but it really depends on the quality. There is a LOT of variation in elk and stag. So some folks may get real nice elk or stag and others might get not so nice stuff. Wood and synthetics are much more homogeneous. Lots of good choices. Just got to weigh the pros and cons.