What's the Truth About Foreign Aid and Development?

I just listened to a radio program with John Perkins, the author of the hit book "Confessions of an Economic Hit Man." Also on the show were 3 other guests with a wide range of positions about the claims Perkins makes in his book. The most last one is a guy from the World Bank who basically completely disagrees. His main point was, well, yeah, there's bad stories but there's good ones too, and of course projects and loans are going to fail a lot because these countries are risky environments. He also spewed out lots of statistics about how the world and its poor people are better off in the last few decades thanks to foreign aid and the IMF and the World Bank, etc. Perkins counters with other statistics that prove just the opposite.

The show's host sums it up by saying "the devil is in the details." Whenever anyone uses that maxim I like to quote Einstein who said the opposite: God is in the details.

But anyway, my point is, if the details are important, but the different sides are tossing around totally contradictory details, how do we decide? What numbers do we believe? How can we, the normal, everyday members of civil society, possibly know what the truth is? on one side are very smart people, even nice people, even a couple people I know personally, who say "capitalism has made the world better, here's the stats to prove it." And then on the other side are other very smart people saying the opposite, and they have convincing figures too.

What to believe? Is this just a matter of faith?