What are the key differences between Audi A3 and A4 sedans?

As a car enthusiast, I am looking to buy a new Audi but I am torn between the A3 and A4 sedans. Can someone highlight the major differences between these two models, both in terms of performance and features?

The Audi A3 is a compact sedan, whereas the A4 is a mid-size sedan. This means that the A4 offers more space and legroom for passengers and cargo. However, the A3 is more fuel efficient and easier to maneuver in tight spaces.

Both the A3 and A4 come with Quattro all-wheel drive as an option. However, the A4 offers a slightly more advanced version called Quattro Ultra, which improves fuel efficiency without compromising performance.