Mash bananas with vanilla in a medium bowl. Set aside.
Combine flour, salt, and baking soda in another medium bowl. Set aside.
Cream the butter and sugars. Beat on high 3-5 minutes, until very light and fluffy.
Add one egg at a time, beating thoroughly after each addition.
Alternate adding banana mixture and flour mixture (about three additions each).
Fill each loaf pan in 3 layers; after each layer, sprinkle on cinnamon. When loaf pans are full, use a toothpick or skewer to swirl cinnamon (do not overmix or the swirls will not be apparent). It is not necessary to use all of the cinnamon; use only as much as is desired.
Sprinkle each loaf with sugar (it will bake into a crunchy, sweet crust).
Bake at 350F 45-60 minutes, until a knife inserted in middle comes out clean.