Few reasons...
Handling, I find it better than other LMP/group C cars. Maybe the roadholding isn't as good, but the turn-in is fantastically lively. The whole car feels twitchy and high-strung. You can definitely make mistakes, but it feels like it is always you letting the car down, not the other way around.
Sound. Is highly accurate to the real car. The wankel engine in itself was a brilliant bit of engineering, the 4 rotor engine in the 787b is the pinnacle of that technology. There is also a very distinct and audible tone change as the car enters redline, the same is true if you are below the powerband, you need never look at a rev counter when driving the 787b.
Looks. The Renown clothing company provided factory sponsorship for the 787 race effort, the design was designed to be as striking and different as the car was. It is worth noting that Renown also made matching clothing for the entire team. Printed in giant text across the rear wing is "CHARGE", that doesn't even need explaining (but I will anyway).
History: The 787B (upgraded engine: B model) was designed to compete in world championship series races (group C), Endurance races, (Le Mans, suzuka 1000k) and the japanese championship series. Thats three different rule sets that the car had to be designed around. The engine was originally dyno'ed at 900 horsepower! However it was detuned to a measly 700 horsepower for reliability. This last point was one that the 787b delivered on in spades.
In their now imfamous 1991 LeMans win the Mazda team feilded 3 cars, two used a conventional technique, but the third (number 55 787B) was told to race balls-to-the-wall, 'forget this is a 24 hour race, pretend it is a sprint race' And so for 24 hours they pushed the 55 car as hard as they could. On the last driver change pit stop Johnny Herbert requested to stay in the car and drive it to victory, double stinting having driven the car at break neck speed the entire time. After all the 55 car's mercedes-sauber competetion had fallen out of contention by (primarily by fragging their transmissions) the 55 787B ran its way to victory. Herbert had to be pulled out of the drivers seat by force and was unable to make it to the podium, so complete was his exaustion.
It was a combination of the skill of the drivers being able to push non-stop without fault, and a car that could take being pushed to capacity for 24 hours straight that made the victory. The sauber cars were shown that speed wasn't everything as it was the car that let them down. Sauber drivers that year included a young Schumacher.
How fast a car laps a track means little in the grand scheme of things, the way the car 'feels' means far more. Feel can come from many factors.
