Can someone explain to me the difference between the Futaba servos? I understand there are different size and torques and major stuff like that, but some of the differences seem more obscure. Like the difference between the S3001 and the S3004. Does ball-baring make a difference? What is all the core-less stuff about?

If this is more than a post can handle, could you provide a refference where I could read about these things?

Zee