The choice depends on the purpose you want to use the lamp for. The looks of these bulbs are the same for all three types. The degrees of the bulbs indicates the width of the beam of light. The higher the amount of degrees, the higher the width of the light beam.

 

A bulb with an opening angle of 8° has a very narrow light beam. The full power of the bulb is bundled into a narrow beam of 8°.

 

This type of lamp is often used to illuminate specific objects, plants, pieces of art, etc. If you place multiple of this type of lamps in a room, you get narrow, separate light beams instead of uniform illumination.

 

A lamp with an opening angle of 24° has a medium sized light beam. The full power of the bulb is bundled into a light beam of 24°. This type of lamp is often used to illuminate bigger objects, or whole parts of the room, etc.

 

A lamp with an opening angle of 45° has a wide light beam. The full power of the bulb is bundled into a light beaum of 24°. This type of lamp is often used for general lighting in a room. If you install multiple of these lamps in a room, you get an evenly lit environment.