Pioneer has been changing the meetings rules and game each month, but since the beginning, the advisors have always had a influential role in determining the winners. The month I Was in the winning batch, I was never in the top 10 rank, but was pushed over the edge in the final evaluation period.
My understanding is that the winners are decided by a combined factor of perceived progress, points, and weighted evaluations by past winners and advisors.
The reason for this is that not all projects can be compared equally. Someone with a funded start up who has a team of 5 should be equally compared to a single founder starting a project in a developing country.
Overall, from the winners I have seen, there do seem to be emphasis on projects that are socially oriented or geographically diverse. One goal that has been expressed multiple times by the Pioneer founders is to create a global campus. Rather than allowing campus driven knowledge and social interactions to be limited to people who have access to coastal cities or urban mega cities, Pioneer provides an opportunity for access to the same social lift, but without the limitations of location.
EDIT: Changed "Ivy League" campus to global campus.