A Magnitude is just a quantitative number while power provides us with sway. We should get it with a model - assume two people are riding a vehicle and a bicycle at a similar speed of 100km/hr.
The individual riding the bicycle will most likely harm the motor at such a speed. Then again, speed won't only affect the motor.
Presently we can say that the greatness of both vehicle and bicycle is the same i.e 100km/hr, however, both will have an alternate effect due to the force. Power changes with the effect while greatness continues as before.