RECOIL magazine has an interesting article from Aaron Cowan on holsters and types of methods to carry. It is a bit long but definitely worth reading it.
Part 1: http://www.recoilweb.com/cowan-on-holsters-part-i-27975.html
Part 2: http://www.recoilweb.com/holster-selection-and-carry-options-part-ii-28017.html
From: RECOIL