Both directional and the omnidirectional antennas have their pros and cons. Taking the omni antennas as an example, it must be said that they have a 360-degree horizontal pattern that allows them to be mounted upside down, they are very easy to install and they can be quickly attached to the product in question, due to their convenient shape. An omni antenna is especially designed to deliver long communications distances, in spite of having very poor coverage below the antenna.
The directional antennas, on the other hand, allow you to divert the RF energy in the desired direction, thus increasing the distance and covering a longer rage. However, the longer the range, the less effective the beamwidth becomes, this is why unlike omni antennas which are very versatile, the directional ones are mainly used for long corridors, hallways and other similar structures, and they are far better for indoor use than for outdoor use. One downside of the directional antennas that does not apply to the omnidirectional ones is the fact that if they do not face in the direction where you aim to get the coverage (which makes them very difficult to install), they are totally inefficient.
Small Omni-Directional antennas made of plastic are the most common type of antenna used in WiFi and wireless applications. Their real name is dipole antennas and they are often called “rubber duck antennas” and rp-sma-antenna because the come with an rp-sma male connector.