Preheat oven to 375°. Lightly grease 12 muffin cups or line with muffin papers
In a large bowl, mix together flour, baking soda, baking powder, salt, nutmeg, and cinnamon. In another bowl, beat together bananas, white sugar, brown sugar, vanilla, egg, and oil. Stir the banana mixture into the flour mixture until just moistened. Spoon batter into prepared muffin cups.
In a small bowl, mix together brown sugar, flour, and cinnamon. Cut in butter until mixture resembles coarse cornmeal. Sprinkle topping over muffins.
Bake in preheated oven for 18-20 minutes or until a toothpick inserted into center of muffin comes out clean.