1. **Travel Requirements:** Firstly, consider your daily travel needs. For regular commuting, it's often ideal to choose an electric bicycle with moderate power and speed. However, if you seek higher speed and power for hilly terrains or long-distance trips, you may require an electric bike with more power and speed.

2. **Legal Regulations:** Different countries and regions have specific regulations governing the speed and power of electric bicycles. Ensure that you understand and comply with local laws and regulations before making a purchase to avoid legal issues.

3. **Motor Power:** Electric bicycle motor power is typically measured in watts (W). Higher motor power provides more torque for quicker acceleration but can consume more battery energy. Choosing the motor power involves a balance between speed, acceleration, and battery life.

4. **Type of Electric Bicycle:** Different types of electric bicycles have varied speed and power requirements. For instance, mountain electric bikes often need higher power to handle rough terrains, while shared electric bikes typically have lower speeds but adequate power for city commuting.

5. **Battery Capacity:** Battery capacity directly affects the electric bicycle's range. If you require higher speed and power, a larger battery capacity might be necessary to ensure enough energy for your ride.

6. **Personal Preferences:** Ultimately, personal preferences play a crucial role. Some riders prefer faster speeds and more power, while others prioritize range and comfort.

When choosing the speed and power of your electric bicycle, it's advisable to consult professional electric bicycle retailers or manufacturers who can provide tailored recommendations based on your needs. Additionally, test-riding different electric bike types can help you find the best fit for you.