As one data point, I can confirm that brushed motors work fairly well for this challenge. The winner at our state competition used 6 x AA batteries running both anEd63 wrote:Brushless motors are great, but a brushed motor is just fine for this event. We're using a brushed motor and battery directly connected and getting times in the 1.75 to 1.80 sec range. We have been the fasted car at both invitationals so far this year. Sometimes simpler is better.
Arduino and a MOSFET motor controller coupled to a 6V motor that also included an encoder. Wheels were pretty small (probably 2.5 inches or so). Time was about 2.2 seconds and was around 5 cm away from the target on the second run.