The prototype's plastics aren't necessarily inferior, it's the soft tooling used for the prototyping run that's inferior. As I understand it, you can only make so many injections before it degrades and the parts aren't made as crisply on soft tooling as on hard tooling.

Re: Soft/Hard Tooling

If a different plastic was used, it wouldn't be a good prototyping test. The reason the prototypes are generally smooth/glossy is that adding texture to the hard tooling is the very last step done in preparation for production.

My M.E. little bro says tooling for injection molding is a black art, it costs a fortune to get it just right. The plastic has to cool enough to be ejected as quickly as possible, shortening the cycle time. Time on the injection molding machine is the most expensive portion of the part being produced.