Compare the Subaru Impreza WRX STI 2.5 Turbo - [2017] vs Audi A3 S3 Sportback 2.0 Turbo S-Tronic - [2016]. Find out which car is the fastest, most powerful, lightest or has the biggest engine in our top trumps style comparison page. Find out which car has the highest top speed or is the fastest accelerating, is it the Subaru Impreza WRX STI 2.5 Turbo or the Audi A3 S3 Sportback 2.0 Turbo S-Tronic. We'll leave it up to you to decide which is your favourite.