Here is why you should:
- Turn higher RPM's (less power loss)
- Lower current draw
- Longer flight time
- Lower vibrations to the airframe
- Servo's will last longer
- Motors and bearings will last longer
- Less stress on the airframe (especially motor mounts)
- Less noise
Let me ask - do you balance the tires on your car? These spin WAY faster, so they are even more important.
When you start you will be amazed how many props are out of balance. There are a couple of good brands but even they can have mixed results.