What are the key differences between the Audi A3 and A4 in terms of design?

I am looking to buy an Audi but can't decide between the A3 and A4. Can someone explain the main design elements that differentiate these two models?

The Audi A3 and A4 have distinct design differences, with the A3 being more sporty and compact while the A4 has a more elegant and sophisticated look. The A3 features a more aggressive front grille and sharper body lines, while the A4 has a wider and sleeker appearance.