When it comes to choosing a DC motor for an electric bicycle, there are several factors to consider, including power, efficiency, size, and cost. Here are some of the most popular DC motors used for electric bicycles:

Brushless DC (BLDC) Motors(36V 48V 7000W 13inch ebike Motor Wheel DC Brushless Motor Scooter Motorcycle): These motorized single shaft brushless motors are highly efficient and offer excellent power-to-weight ratios. However, they are typically more expensive than brushed DC motors.
Brushed DC Motors(High Power 13 inch Hub Motor 2000W 48V 60V 72V Scooter Moto Bicycle Single Shaft): These motors are less expensive than BLDC motors and are a popular choice for DIY electric bicycles.

Geared Motors(High torque 13 inch electric 170KM/H gear motor 60V 72V 96V 7000W hub motor 70N.M scooter UTV): Geared motors are designed to provide more torque at lower speeds, making them ideal for electric bicycles.
Hub Motors(12 inch 48V60V72V brushless single shaft 2500W split motor bicycle scooter 100km/h): Hub motors are mounted directly to the bicycle wheel hub and provide a simple, low-maintenance solution for electric bicycles.
Ultimately, the best DC dual shaft hub motor for your electric bicycle will depend on your specific requirements and preferences. Be sure to do your research and compare different options before making a decision.