Dubya writes “what are the differences in hard rubber vs wood for clarinets? I know plastic is the student model material, but I’ve seen pro stuff in both of the others. Is there a quality difference, or is it more up to preference? What would guide those preferences?” 

I can’t think of any “Pro” clarinets that are made of rubber. Never heard of such a thing. There are clarinets that are made of wood, wood and carbon fiber (called Greenline by Buffet), or ABS Resin (Plastic). None of these are rubber. Wood is the way to go. If you live in an area where cracking could be a problem, or are playing in situations where cracking might happen, the wood/carbon fiber is the way to go. Plastic is for student models. Wood simply gives you a better sound, and the cracking potential is very low. So get a wood clarinet.