This article explains the difference between corned beef and pastrami. To me, the big difference is that no matter what restaurant or deli I eat in, I always find the corned beef quite edible but occasionally find the pastrami too spicy. Once in a while, I find them close to indistinguishable. So if I'm going to order either, I go with the corned beef. And yes, I've tried the pastrami at Langer's in downtown L.A.