Is there a difference or is it just some name sake done by kennel club to seperate the show lines from the working lines?
Do show lines make just as good working dogs?
Have a look at http://www.bordercollierescue.org/
and go to the breed profile area (can't remember exactly what it is called) and this will give a good explanation. As to show dogs making good working dogs I suppose it is how you define "good" and what your expectations are.