Hi,
We have a Koolie and a BC, both of which are only 7 months old. They work in completely different ways. "Chance" (no relation to the other Chance listed) is a red merle Koolie. He works very very fast always running and seemingly tireless. This does stress the sheep out a bit and as Chance and I are both beginners we are working on slowing him down and stopping the constant barking.
"Jenna" the BC is much slower, works wider and seems to have more "control" of the sheep. She works with eye and attitude rather than speed and noise.
From watching Kelpies, BC's and Koolies all working 1 after the other I have noticed that BC's work wider and dash in for a nip every so often but generally have great control of the sheep through eye and personality.
Kelpies stalk and eye as well but tend to work closer to the sheep and are more fond of moving than standing still like a BC. They are also more vocal.
Koolies are like dogs on speed. They love the work, but treat it more as a game. They still get the job done but seem to need the sheep to do something at all times and don't like them to be still. They seldom stalk or directly eye the sheep and are fond of body slamming rather than nipping.
Mind you these are my own views as a beginner and should not at all be taken as gospel.
Adam
P.S. We are going out to have some fun this weekend so I will try to get picks of different dogs to demonstrate what i mean.