Saigon bánh mì has crustier bread, more pâté, and bolder chili than Hanoi's. Bánh Mì Huỳnh Hoa is the cult favorite.
Expect a queue. The 'thập cẩm' (everything) version comes with multiple cold cuts, pâté, and a generous chili kick.
For a lighter version, try Bánh Mì 37 Nguyễn Trãi or Bánh Mì Hồng Hoa. Both have decades of loyal regulars.