In the blue corner, there's the super-sexy i8. Even though everybody thinks it's a supercar, the flagship of the i range has a 1.5-liter engine with only three cylinders. While it might be similar to what the MINI Cooper has, the output is more along the lines of a JCW. Couple that with an electric motor that drives the front axle and you have one of the most interesting coupes on the planet.
By comparison, the M4 seems normal. It too has some advanced features, such as the first twin-turbo engine BMW has offered in this segment (an M compact). It's a 3-liter unit that offers more power than the i8 can muster: 425 hp vs. the hybrid's 357 hp (US market figures).
So how can this possibly be a close race? Well, hybrids are usually heavy, but BMW invested a lot of money into making the i8 from something called carbon fiber reinforced plastic. The sturdy yet light material means the i8 is about 300lbs less than an M4 coupe when they hit the scales. Torque is similar, slightly favoring the M4. However, everybody knows that electric motors have no lag, which is a huge advantage in a race.
On paper, the M4 is faster, but you can't trust a company like BMW, who needs to make several awesome machines that don't trample all over each other. After all, what do you do when a loyal customer asks you why his M4 lost a race against a hybrid?