I'm not quite sure what to get CAO, sarplaninac, or CO. I have owned large breed dogs before including, german shepherds, st. Bernard's, malamute. Which one would be most suitable for me? It gets cold here in alberta. But all these breeds can do fine in about any weather. But I live on four fenced acres and am having problems with both people and animals. Although my problems are mostly about wild animals. I don't necessarily need a lgd but need something strong enough to confront man and animal. 

Tell me if these breeders are good? 

Sarp: http://www.grazerie.com/sarplaninac 

CO: http://www.courageouscaucasians.com/ 

CAO: http://www.alabaiusa.com/ 

They all say they are working animals which is what I am looking for. So which animal would be best for me? Are good working sarps just as formidable and good as workers as CO and CAO? Which one would be right for me?