Audi A4 is a more powerful machine then Audi A3. Audi A4 comes equipped with 3 Zone climate control, Variable Head Restraints For Front Seats, Rear Seat Backrest, FoldingSun Visor, Audi Drive Select Rear Seat Bag, etc. Moreover, you can click on the link to see the complete comparison. Also, we'd suggest taking the test drive so that you can understand the difference - Car Showrooms
For this, we would suggest you walk into the nearest authorized service centre as they will be the better people to assist you. You can click on the following link to see the details of the nearest service centre and selecting your city accordingly - Service centre