I may need to put a flame suit on, but I am starting to doubt the need to use any rub on a big pork butt. The flavor doesn't go more than, at the most, a half inch into the meat, so when you slice it or pull it, you're not getting a lot of that flavor in the meat you eat.
Pork butt is just such a big, thick chunk of meat. I focus on getting it cooked just right, and then serve it with lots of flavors, whether it is a PP sammich, or some carnitas style tacos, or Cuban style roast with beans and plantains.
Am I alone on this?