You can slice pork shoulder, even with bone-in butts. It actually doesn't take as long to reach a semi-tender state for slicing as it does to reach a pulling tender state. The last sliced butt, or maybe the first, that I documented here:
http://www.smokingmeatforums.com/t/...-rub-2-butts-recipes-q-view-1-sliced-2-pulled
Pork Tenderloin is a smaller muscle which is similar to the beef tenderloin...some might call it the cut of pork fit for a king. It has a very small cross-section, so small slices will result. It has no fat-cap and is relatively lean, so not very forgiving if overcooked. Cook to temp of 145* minimum and rest before slicing.
As for a better cut of pork for slicing, boneless pork loin is among the better buys for the money. It has a large enough cross-section to make for a chop-sized slice. If taken to the minimum recommended internal temp of 145*, and, properly rested before slicing and serving, there will be more than adequate natural moisture in the finished product, regardless of cooking method or equipment. I have taken them all the way to 160* (the previous minimum recommended internal temp) and it still yielded a very moist product. Loins are not as forgiving as the shoulder cuts if temps run away on you a bit, as loins have far less interior fat and generally have a trimmed fat-cap, but if you keep tabs on your temps they will reward you with a milder flavored slice of pork. Flavor being the main difference between the should and loin, I find sliced shoulder to be more to my liking...it yields layers of deeper and stronger flavors from different muscles.
Eric