Fiberglass antenna Gain explaination
Low gain antennas (3 dBi) have a broad radiation pattern and are best for rugged terrain or a dense urban environment. Your signal is less likely to be blocked by obstacles such as buildings and hills tight to your location.
Medium gain antennas (5dBi and 5.8 dBi) have a more rounded and broader pattern. These antennas work well around obstructions and are great for suburban areas. In addition, they would allow you to connect with hotspots that are both vertically and horizontally near you.
High gain antennas (8dbi and 10dBi) radiate in a narrow pattern for a longer distance and are great for flat terrain with few obstacles. However, if your antenna location is high, your signal may overshoot anything below you. If your antenna is low down, obstructions may block your signal.