Sometimes it's hard to make the right decision, just ask the now former Detroit Lions general manager (not to be confused with the other GM in town, you know, GM) Matt Millen. Without much in the way of NFL executive leadership experience he stepped in to head a team that, since, has had a bad record even for an organization based in Detroit. They're 31-84. They're 53 games below .500 after playing only 115 games. That's bad. Even Bill Ford, Jr lost faith in Millen, and he ran Ford Motor Company for like two years. It's hard to point to one thing he did wrong, but first-round draft picks are one place to look. Joey Harrington? Really? When we asked to name your favorite video game car commenter The Stig's Fat American Cousin stepped up with the kind of thought Millen should have probably put into running the Lions.
Clearly, as far as Mario Kart goes, you can't beat the original one on the SNES. And anybody who has ever played that knows that Koopa Troopa is the best kart. He's light and has great grip in the corners, without sacrificing too much top end speed or acceleration. But of course, Toad is actually just a badge-engineered Koopa Troopa... Princess and Yoshi, have the best off the line acceleration, but seem to struggle through the corners. Having less grip. Perhaps they prefer to run harder tires, a good strategy to use less tires while everybody else is hitting the pits, though not such a good strategy in the typical 5 lap race... Either way, you can easily get to the head of the pack off the launch using these two. Then you have Bowser and Donkey Kong. Their strengths are their mass and top speed. If you believe in the philosophy, "rubbing is racing" then these guys are the karts for you. They make it really easy to bump other karts out of your way. Causing you not to get hit off the edges of tracks like "Rainbow Road" and the "Ghost Valley" series as well. Cornering is definitely not their strong point though. With heavy understeer tendencies, powersliding into the corner well before the apex can keep you on track without losing too much speed. Also remember, these guys have the highest top speed, and lowest acceleration. Keep the momentum going and you're sure to win. Mario and Luigi are also great karts to use. They're well rounded characters who are best suited for more advanced players. They have the second highest top speed of all the karts, but don't sacrifice anything in terms of cornering if you really know how to drive. While they will oversteer quite a bit more than Koopa Troopa or Toad, it's easily controllable. So the best kart, is definitely subjective. Consider your driving style, and your experience when choosing a kart.
If that's not "blue shell" thinking, we don't know what is.