No one component defines the performance of the fan; rather it is the combination of all of these components that affects how well a fan works.

Motor

Basically, there are two types of ceiling fan motors: those with sealed and lubricated ball bearings and those with bearings that rotate in an oil bath. Lubrication provides smooth operation and contributes to the longevity of the motor. Motors with sealed bearings require little or no maintenance whereas motors with oil baths need occasional service, such as adding oil.

Motor Grade

• Performance Grade fans Use larger and more powerful motors that are designed for continuous use and quiet operation. These are usually the most expensive models
• Medium Grade fans are suitable for operating 12 hours or less per day.
• Moderate or Economy Grade fans work best in a room with 8-foot ceilings, running no more than 8 hours a day. Least are the most inexpensive ceiling fans

Motor Housing

The housing is the decorative body of the fan that encloses the fan motor. Fans that use heavier materials, such as die cast metals, for housing tend to vibrate less, provide more stability for longer downrods, and provide a good surface for high quality finishes.

Other features that ensure longevity and quiet operation include heavy-duty windings, precision engineering bearings, and shock-absorbent internal components. These features are commonly found in more expensive ceiling fan models.

Blade

• Pitch is the angle of the fan's blades, and it's measured in degrees. Higher blade pitches usually move more air, which is given in cubic feet per minute, or CFM. However, blade pitch alone does not determine air movement. Other factors such as the motor design and speed, as well as blade design, material, number, and length can contribute to the amount of air movement. Higher pitch is NOT always better -  some models offer a higher blade pitch to compensate for a smaller, less efficient motor.
• Blades should be sealed from moisture to prevent warping, bubbling, or peeling. Some manufacturers offer special coatings on metal finishes to prevent scratches or tarnishing.
• High quality blades are weighed and balanced prior to shipment and come in factory-matched sets. For this reason, they cannot be switched out with other fans. For flexibility in design, a number of manufacturers offer a variety of blade styles and finishes for a particular fan. However, changing the blade style could affect the performance of the fan.

Controls

Most residential ceiling fans (and all ENERGY STAR qualified fans) feature the ability to reverse the motor and airflow direction, allowing you to operate your fan year round. This control is usually found on the fan's switch housing.

source: U.S. Department of Energy