Just to add on, American Deli Pastrami is traditionally made out of navel or plate, which are fattier, not brisket. Pasttrami is usually coated with a black pepper rub before it is cooked, and whereas corned beef is usually braised, pastrami is traditionally smoked and then steamed. (I think a cold smoke may be more traditional). Montreal Smoked Beef is smoked like pastrami, but hot smoked, without the steam bath, and is traditionally brisket. That's why I'd say that smoked corned beef is closer to it, though the MM spices are closer to pastrami IMHO.
Of course british "corned beef" is something different all together.