What if you are a small country that does not have the luxury of operating 2 platforms. And you need an aircraft for CAS, which would u chose for operating against factions and insurgencies? or does the A-10's ability not overlap with the tiger/apache enough to be able to replace it?
To operate only one aircraft type you'd pick a multipurpose helicopter. There is no point having close air support for your troops if you do not have a helicopter to transport your troops.
If the country is small then a helicopter can reach any point rather quickly. The transit speed of the A-10 is much quicker but you'd have to start traveling longer distances for transit speed to make a difference. A helicopter can take off quicker and from bases further forward offsetting the transit speed.
The sheer cost of operating an Apache or A-10C would be out of reach of most small countries. The Super Tucano is a better option if you already have a utility helicopter for transport duties.
Just as an A-10 could perform some Apache missions, an Apache could perform some missions used by light scout/utility helicopters. These missions may not be able to be performed by an A-10.
Any country that operated a fixed wing platform would always have an existing helicopter fleet. So if you were limited to one platform it would be a utility helicopter that could be used for light gunship duties as well as transport. To operate a single aircraft you would never choose the A-10 as it cannot transport troops and supplies.
An A-10 and Apache is fairly specialised and you would not consider buying these systems unless you were operating multiple platforms. If you have a utility helicopter and transport helicopter then you may consider a dedicated gunship. However a light trainer such as the Hawk may be a better all round option as it could provide air defence if required.
These are only suggestions, everyone has a different requirement.