i guess it depends on the voltage that you apply to the motor. there is no way a 4300 is keeping up with a 19 in 1/12 with only 4.8 volts, the motor is only going to run 20,640rpm. Any stock motor will do that and you don't need to be eddie. lol
But the brushless does have more torque and the biggest part is that it does not have the drag the brushed motor has. I have run the 4300 with stock for a couple of month, and the notable difference is how far the car is through the corners. it gets around the corners faster and also out of the corner faster then a stock, but down the straight, I am not as fast as teh brushed motors. so if the track is mostly straight's you will have a good run for your money, with a lot of tight corners, the brushless will definatley kill the brushed.
and with the number from above, there is no way a 4300 will keep up with a 19t. no a 5800 gets closer, 27,840rpm at 4.8 volts. but then a good tuned 19 is closer to the 29,000. my guess is that torque would be about the same for 19t and 5800, but again the 5800 is like a low turn mod, not motor braking or drag in it at all.
the thing to remember is that applying more voltage to a brushless, at least to a point, the rpms increase linearly, to a brushed motor, they do not. so if you are looking at sedan with 7.2 or lipo with 7.4 the 4300 will do 30,960 - 31,820