Some of the price difference that you see between the A3 and A4 comes down to the fact that quattro AWD is standard on the A4, but not the A3. Adding quattro to the A3 closes the gap a little but the larger A4 is always going to be a bit more than a similarly equipped A3. Size is really the big distinguishing factor when it comes to these two cars. But your passengers are unlikely to notice a real difference in size as you can see from the nearly identical legroom. The size difference comes down to a slightly tighter turning circle for the A3 and a bit more trunk space for the A4.

Most of the remaining differences between these two models come down to matters of taste. Both have 17-inch wheels as standard with 18-inch options available but the designs are different. The A3 has concealed exhaust outlets while the A4 has chromed dual exits. Inside, the MMI infotainment touchscreen in both models is 10.1 inches but the location on the dash is different. Both come with a standard power sunroof but the A3's is bigger. Lastly, the interior trim inserts are different on these models. This is completely aesthetic but maybe that's the one deciding factor for you to choose one over the other.