mostly the AR platform style gun will be a .223 used for coyote or varmints etc. But there are plenty of calibers in that platform now since they have become a very wanted and liked weapon for numerous reasons. But I would say the pros would be the accessories you can add to them. You can turn any AR style gun into anything you want. From sights to stocks to lights and magazines its crazy. You can start with a stock AR platform and turn it into the best coyote (or any animal specific) ever. Cons I would say like the other guys have said is the weight especially after you start adding all kinds of stuff to it. Also once you add things to it it might start to get awkward to shoulder or hold while hunting as opposed to just shooting from a rest. And like he said above ^^ cleaning it will become a pain. But I think there is more pros than cons and the way I look at it, creating a personal gun specifically for one main reason(hunting coyote or hunting deer or shooting for fun) is where all the fun is at. Good luck with it. The options are endless.