A holster has to be comfortable and fit the gun, hold the gun in the same place all day or night, keep it close to your body as you set down, stand, run, or drive. I do not have to adjust mine if I get in the car or set down. A good belt is also needed and I spent more on the belts then the holsters. It should allow a fast draw and you should be able to re holster the gun with out looking or using both hands. In the past I have been pro Galco due to quality and price. I have also had a couple of custom made holsters. (big bucks but only copys of galco or other known makers) I have a 5" barrel and a 3" barrel. The holsters I have had allow me to change guns with out changing holsters.
I have a new holster that meets all of my requirements, and is more durable then leather, guaranteed for life and more effecent then the 3 leather ones i have, (it allows me to cant the gun), It was not inexpensive it was cheep, It adds 2 oz to the weight of the gun and adds less bulk then leather.
Check out FOBUS holsters