This may be a very simplistic answer - but the best LGD it the one that guards your livestock and protect them from harm. Ok, that was really simple but you have to consider the variables that define the best LGD. Such as livestock, range, containment, climate, size, type of predator or threat, operating environment, training, owner participation, nutrition, the breed, and the dog.. yep there are many more variables but those are good for starters. So, if your dog protects your flock to suit your need then it is the best LGD for you. It is an individual assessment of the dog against what is expected of it that determines which is the best for the observer. .. was that confusing?