I think money should be spent on things where it can generate the most return.
This is one of the most basic economic theories.
I firmly believe that this should be the case in the instances of charity.
Well, if we disregard the idea of utility curve (or the idea of individual definition of "happiness"),
charity generates the most value of money - especially charity that are directed to emergencies and where USD exchange rate incurs the most value (e.g. Sub-Saharan African states). Charity spent on such regions can bring life to those who were imminent to death - literally. How can you compare a life with monetary return on a stock investment?
For this reason, I firmly believe now that it is rather wrong to argue with logic that charity for a certain group of unfortunate is better than other uses. For example, I often see Koreans arguing that Koreans should spend money for unfortunate Koreans rather than unfortunate non-Koreans. This is just an example although this is something a true story. There are Americans arguing the same thing for charity directed to Americans. If you believe such is true, then donate your portion of income to charity of your belief, but don't try to argue that others are wrong not to do the same.
I know any value of money spent for charity is valuable, but once you start such dumb arguments you are bound to lose logically, because $1 can do so much more in, say, Zimbabwe than in America.
However, the idea of utility curve changes all that.
Although I try to keep all my decisions logical, I am also very much affected by my own utility curves, or region, actually. But I should note that even with idea of utility curve, you cannot make such argument because one's utility curve is very unique and it's only infinitesimally possible that there exists another with exactly the same utility curve.
But I am never going to forget what charity can do for those in need in general.
Once my life is set, charity will always be one of the most important parts of my life.
