What are the main differences between the Audi A3 and A4?

I'm considering upgrading to a new Audi and I'm torn between the A3 and A4. What are the major differences between the two models?

The Audi A3 is a compact luxury car while the A4 is a mid-size luxury car. This means that the A4 will have a slightly larger interior with more room for passengers and cargo.

The A4 also has a more powerful engine, with a base model offering 188 horsepower compared to the A3's 186 horsepower. This may be something to consider if you're looking for a more high-performance vehicle.