Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x5-inch loaf pan.

Combine flour, baking powder, baking soda, and salt in a large bowl.

Combine sugar, brown sugar, and oil in a separate bowl. Stir in buttermilk, egg, and vanilla extract. Add to flour mixture and mix until combined. Fold in chocolate chips. Spoon 1/2 of the batter into the prepared loaf pan.

Combine brown sugar and cinnamon for the topping in a small bowl. Sprinkle all but 2 tablespoons topping into the loaf pan and cover with the remaining batter. Gently drag a knife through the batter to create a swirl. Sprinkle the remaining topping on top of the loaf.

Bake in a preheated oven until a toothpick inserted comes out clean, 50 to 60 minutes. Remove and let cool for 15 minutes. Remove from the pan to a wire rack to cool completely.