The best cut of meat for pork carnitas is the pork shoulder. The large amount of fat in a pork shoulder is what makes for easily shreddable, juicy, and delicious carnitas. You could use either a bone in or boneless pork shoulder! The bone could add more delicious flavors and after braising will be super easy to remove. But using a boneless cut will make preparing the pork quite a bit easier. So it is up to you! Pork butt or "boston butt" is a good alternative and can also be used. However, a lean cut like pork loin won't produce the best results.