The Audi A3 uses a mild hybrid setup that produces 201 horsepower and 221 lb ft of torque. Power is delivered smoothly and quietly. Stop and go traffic feels calm. Highway cruising feels light and easy. The BMW 2 Series offers more power but it comes from a traditional gas engine. That extra punch can feel fun but it can also feel less refined in daily driving.
Fuel use is very similar between both cars. The Audi A3 delivers 8.5 L per 100 km combined which keeps fuel stops reasonable. The BMW is only slightly better on paper. In real life the difference is small. The smoother hybrid feel of the A3 often feels more enjoyable.