I have had the pleasure of owning all of the above (plus a couple of other breeds), and my choice would be the Austrailian Cattle Dog (or commonly known as the Blue Heeler, and yes, I know they aren't mentioned above). They are smart, and always on the go - and kept up with my kids, while making sure they are well guarded. (NO ONE would dare come in the yard without me being there)
But my heelers have passed away, and I currently have Border Collies - and yes, they are hyper, but they are my shadows, and they love to work. Nothing gives them a bigger pleasure then a scratch and a pat on the side when they get a "well done". I don't find them as smart work wise as the Heeler, but they figure things out after doing the same job a few times.