Prepare the pans: Preheat oven to 350°F (175°C). Grease and flour two 8½ × 4½-inch loaf pans.
Mix dry ingredients: In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
Cream butter and cream cheese: In a large mixing bowl, beat softened butter and cream cheese until creamy. Gradually add sugar and beat until light and fluffy.
Add eggs: Beat in eggs one at a time until just combined.
Combine wet and dry: On low speed, add the flour mixture gradually until just blended.
Add bananas, nuts, and vanilla: Stir in mashed bananas, chopped nuts, and vanilla extract. Divide batter evenly into prepared pans.
Make topping: Mix brown sugar, pecans, flour, butter, and cinnamon in a small bowl. Sprinkle evenly over both pans of batter.
Bake: Bake for about 1 hour, or until a toothpick inserted in the center comes out clean. If the topping browns too quickly, tent loosely with foil in the last 15 minutes.
Cool and serve: Let loaves cool in pans for 10 minutes, then remove and transfer to a wire rack. Slice and enjoy!