Pastrami may be smoked, but a lot of it can leech out during the steaming process. After you smoke , you have to steam it until (i forget the temps, sorry) it becomes tender and very slice-able. When you go to an old school deli and you look at the counter, they're pulling out big briskets from a steamer, then slicing.
Not exactly sure why the montreal stuff tastes smokier. Probably a heavier application of smoke (d-uh).