What engine is better 18 2 speed or 21 single speed for nitro RC cars?

The choice between an 18 2-speed engine and a 21 single-speed engine for nitro RC cars depends on your driving style and needs. The 18 2-speed offers quicker acceleration and better handling on tight tracks due to its ability to shift gears, making it suitable for racing. In contrast, the 21 single-speed engine provides more torque and speed at higher RPMs, which can be beneficial for open tracks with less need for quick acceleration. Ultimately, the best option depends on the type of terrain and racing style you prefer.