The V8 is not just a power upgrade
The Defender V8 also comes with extra goodies that go beyond raw power. It boasts a unique suspension and transmission tuning. better-suited for the speedy driving that's a byproduct of more than 500 horses under the hood, including a new Dynamic mode in the Terrain Response System.
It also gets a larger anti-roll bar, a unique electronic active rear differential and a yaw controller to allow "fine control of the cornering attitude." In other words, this Land Rover should drift.