The variation in quality of a pastrami (or smoked meat) can indicate simply that it is a natural product. These days the fat content in beef can be so low as to render an ordinarily prime cut of meat into something that will tast like crap and be dry no matter how you cook it. Brisket which is normally a though cut of beef thus will feel this the most. Variation of fat content will make the brisket feel too dry at times alright at other times. The variation of fat content will also negatively affect the cooking time. Less fat will make the meat more vulnerable to overcooking leading to dry stringy meat. It is easy to find more consistancy in mass produced chemically balanced water pumped pastrami. This stuff will consistantly taste blah. The last industrial smoked meat, in my case, I tried had the consistancy of a cellulose sponge. It was very scary. Hand slicing pastrami (or smoked meat) is the only way a restaurant should serve it. Always expect to get a dry sandwich if you order it lean.