It's a complex subject. For a lot of actual performance tested results, try the
Building Science Corporation at:

http://www.buildingscience.com/resources/homeowner.htm

There is a section on basement insulation methods. The bottom line is that the
only insulation type that works is rigid insulating board, but you need to
study the issues on vapor barriers and moisture dynamics in the reports to see
how it applies to your situation

Dennis