Moha,
“Vertical Beam width” & “Half-power Vertical Beam width” are the same things.
For hilly terrain, it is very important to plan your cells not on the top of the hills, but rather in the valley, in order to limit your coverage. Otherwise you’ll have problem with your frequency planning.
If you do this, you can choose antennas with a a “wide” vertical beam, such as 9° or more, in order to cover the valley and also the side of the hills (if needed).
If you decide to put your cells on top of the hills, then you should choose a narrow vertical beam width 5° or 7°, and install those antennas with a lot of tilt.
Best Regards,
Pix