I'm gonna answer your question with another question.
If you gave Masami Hirosaka or Brian Kinwald an Old RC10 or Losi XX, and you had a B4 or XXXcr, whould you beat those guys??
Yes, those cars are still competitive, I run a losi XX against B4,XXXcr and RB5 and I keep up with them, with no problems.
As long a your driving skill are good enough, and the car is set up correctly,
b2 and b3 are still competitive, specially on dirt oval.