The differences between pastrami and corned beef lie in how they are prepared and processed, the specific cuts used, the seasoning blends, and even how they're sliced and served.
Corned beef comes from the flat cut of the brisket, and therefore has its fat mostly along the exterior. It's brined with pickling spices, and then boiled.
Pastrami is also made from brisket but typically uses the point cut, the shoulder, or navel, so the fat is more evenly distributed. After brining, pastrami is smoked and seasoned.
Corned beef has a savory, briny flavor with subtle spice from the pickling blend, and is often sliced thicker and served warm. It's featured in dishes like the Rueben sandwich.
Pastrami, with its smoky flavor and additional spices, is usually sliced thin for sandwiches. Beyond sandwiches, you can use it in tacos, quesadillas, or even on top of fries.