Mario Kart 8 has the largest cast in the history of the franchise. Racers from the length and breadth of the entire Mario universe in its starting roster and the diverse cast of unlockable racers earned by playing through the Grand Prix mode allow players an enormous variety of potential drivers for the equally diverse customizable kart and bike line-up.
Racers in Mario Kart 8 are divided into five categories: Featherweight, Light, Medium, Heavy, and Cruiser. These weight classes are one of the key determining factors in kart and bike performance, influencing how you take and dish out contact with other racers, how well you drift, how much you benefit from drifting, how powerful your Mini-Turbos are, and how well you recover from getting struck by items. As a general rule, lighter-weight racers tend to have great acceleration and cornering, but suffer from lower top speeds and a tendency to get pushed around with great ease by heavier racers. The heavier racers have the highest top speeds in the game, but have issues with cornering, and their acceleration is very poor. Of course, a heavy racer can easily shove aside any smaller and lighter opponent!
Your choice of racer definitely has an effect on how well you can race, but personal preferences figure in heavily for Grand Prix racing. However, when it comes to Time Trials, your choice of racers becomes narrower, as you attempt to optimize your chances at breaking speed records.