geo climatic factor ? i know the rain can have a serious influence on the radio propagation (up to 3 to 6 dB), so it is smart to take in to account the “average amount of rain drop in the country” for your pathloss computation.
Vertical / Horizontal diversity :
horizontal is more efficient (less separation distance needed for the same amount of Rx Gain), but sometimes the antenna support cannot stand horizontal separation mounting. Therefore, in such cases, you have to use V-diversity.