What are the most effective micro-finance institutions
Here is a ranking of Micro-finance institutions from Latin America & the Caribean:
I think this one is the actually most up to date ranking/comparison of micro-finance institutions:
This ranking from MIX, could potentially be helpful their criteria (known as social performance indicators) has 11 criteria.
You can go to Mix Market and sign up (for a free membership for a basic assessment)
They also seem to have a pretty extensive global data.