The 2.5X scopes are more for guys hunting very large and dangerous game at very close ranges found mostly in Africa. Open sights still are the norm there but, someone wanting a piece of glass would use something like these.
The 2.5x scopes are selected,because they allow for quicker target acquisition than a higher power scope.
The fixed 4X would be more common in North America for a faster gun.
Regardless of where you hunt,the 2.5x will allow for quicker target acquisition.