I just came across this about the difference in Picnic vs Boston...
"Boston butt comes from high on the hog, above the shoulder blade, and has lots of juicy, marbled fat. This is probably what most people buy when they purchase pork shoulder in a grocery store. It's a versatile piece of meat that you can just as easily roast or braise. For home cooks, it's also very inexpensive.
Below the butt is the pork shoulder. This cut includes most of the hog's front leg quarter. Because the leg muscles work a lot more than the back, the meat is a little tougher here than the butt, thus requiring a bit more time to coax out tenderness.
A shoulder cut with the shank -- or hock -- attached is called a picnic ham. This cut is cheaper than most because it requires less butchering and has more bone in it. Picnic hams usually come straight from the abattoir in a clean, cryovac'd package, all ready to go.
A picnic ham is what East Coast uses for their pulled pork. Barbecue restaurants that make a lot of pork will go this route because it's cheaper than Boston butt -- but also because some prefer the flavor. The shank and leg, if cooked properly, is full of flavor (what's that old adage about meat next to the bone tasting better?). It also has a great texture to the meat that will stand up to smoke a lot longer than Boston butt. That's probably why East Coast's pulled pork has some bite to it. It's not just a mess of soft, stringy meat -- it has serious meaty texture."
