If I understand correctly, you're asking about pork butt and pork shoulder. If that's indeed the case, they're actually the same thing. On a whole pork shoulder, they're often cut in half at the processor to break them down into two smaller components. The bottom half is referred to as a picnic ham, and the top is referred to as a pork butt, Boston butt, and I'm sure there are likely other names for it as well. Most people cook the top half, or the butt. It has great marbling and is outstanding for long, slow cooks due to the fat content.
Randy, That does help. I know the "butt" is actually part of the shoulder. I was in local grocery store and they had butts for .99 cents a pound but also had shoulders for the same price but obvious different looking fat structure and I was wondering which is better and why?
Bob, Thanks for the Welcome!
If I had to venture a guess, I'd think one was boneless and one wasn't, possibly? Very rarely do I see a picnic ham portion of the shoulder in a store, so I'm thinking that they just had different labels for ways they cut and packaged the same pork butt. At my local grocer, I'll often see a boneless pork shoulder, Boston butt, shoulder roast, etc, and all referring to the same exact cut in their shop. Just a theory, not necessarily the right one
But basically, Randy had it right. A pork shoulder may be cut into to parts -- the upper is the Boston Butt, the lower the picnic. Both are similar in content/texture, pricing and may be bone in or not. But most that I've seen respond to the question seem to prefer the Boston Butt (I certainly do).