What is the difference between a big mac and a grand mac?

The only difference in the new sandwiches is the size — they both are dressed with the ubiquitous lettuce, American cheese, pickles, onions, and special sauce and served on the traditional sesame seed bun. The Grand Mac comes on a bigger bun and features two 2.7 ounce patties, which makes it a one-third-pound sandwich. Something in common is that they are both very nice.. juicy.. sweet.. and delicious..