While the i-Pilot is compatible with both Terrova and PowerDrive V2, my recommendation is to go Terrova.
First, the installation was clearly designed with Terrova in mind. It will take 5 minutes, TOPS, to install i-Pilot in a Terrova. PowerDrive V2s will require significantly more effort to install i-Pilot.
Second, the foot pedal retains full functionality with Terrova, while the foot pedal is completely overridden by i-Pilot in PowerDrive V2 motors.
Field test information on i-Pilot, including a short article on installation in a Terrova (with pics for each step of the install process), can be found at the website below:
Introduction to MinnKota's i-Pilot