If the UN had all the money it could dream of, then on a broad scale, humanity would be much better off. The Red Cross would become redundant, and Médecins Sans Frontières would be rebranded as a UN initiative and expand to effectively serve all who need help. However, you can feed a population, clothe them, and raise their quality of life, but without hands-on education, this can never be sustainable. Social entrepreneurship would still have a very prevalent role in sharing the knowledge and expertise of the first world to those less privileged. As an added bonus, said social entrepreneurs would learn valuable lessons abroad that would serve them well back home.
What sets social entrepreneurship apart from the UN is that it is capable of having a more tailored approach than a massive organization can usually manage. With an emphasis on teaching locals as opposed to simply dumping resources and leaving, social entrepreneurs (like the Arc Initiative) have a lasting, positive effect on the group they target.
As well as helping others, social entrepreneurs better themselves through helping those less fortunate, and learn lessons that can be applied back home, all of which benefits the world in ways that a fully funded UN simply couldn’t.
Sources:
http://www.sauder.ubc.ca/Global_Reach/ARC_Initiative
http://www.un.org/en/strengtheningtheun/