The Motivation Question: Arguments from Justice, and from Humanity

Which of the two dominant arguments for duties to alleviate global poverty, supposing their premises were generally accepted, would be more likely to produce their desired outcome? I take Pogge's argument for obligations grounded in principles of justice, a "contribution" argument, and Campbell's argument for obligations grounded in principles of humanity, an "assistance" argument, to be prototypical. Were people to accept the premises of Campbell's argument, how likely would they be to support governmental reform in policies for international aid, or to make individual contributions to international aid organizations? And I ask the same question, mutatis mutandis, for Pogge's argument.