The truth is probably that they need both programs. However if picking one it is the food programs. The reason is the drought issue will fix itself naturally over time. The hunger issue has been going on forever. If we fix the hunger one then over time the drought should take care of itself.
I think that Africa is in a position that just needs help wherever they can get it. Whether it is food or water, they need some sort of supportive infrastructure. The problem is that no long term help can come from the outside, they will let it fall apart, it has to be a national change.
This is difficult to answer as both food and water are needed. Food is difficult to grow with so little available water. Food is also scarce and hard to preserve, but there is very limited access to clean water for drinking, planting and other basic needs. People are starving and suffering without both.
I believe certain African nations would probably be better of with rainwater programs to alleviate drought. It may also help to show them proper ways to keep water clean or get it clean, since drinking water is such a huge problem in some areas. This could help in two ways, because if they have a decent water supply, they may be able to sustain some crops, which would in turn provide some food.
The food issue in Africa has been ongoing forever and no matter what is tried it does not solve the problem. However I do believe we can make great strides with the drought issue and we should put all the resources to fixing it. It is a goal that will have an end game.