Aside from their exterior designs, the 2021 WRX and WRX STI share a lot of similarities. Both models come with a 270-hp 2.0-liter flat-four engine that can achieve 0-60 mph in just 4.3 seconds and a top speed of 186 mph. They both also feature a six-speed manual transmission and All-Wheel Drive for optimum performance on the street or track.