It is amazing the various answers I received when I asked a similar question. I found it interesting the comments from individuals that had several holsters for the same weapon. The conclusion I quickly came to is choosing a holster is definitely tailored to you and your requirements.
I had planned on trying different holsters from various companies that gave a two-week to a month trial period and would refund me 100% if I did not like their holster. First up was AlienGear (AG). Since I routinely carry 12-14 hours daily and I carry a bug, I wanted a system that could handle both. I have a Milt Sparks IWB for a P229 .40 that really wasn't that comfortable because of the rough leather being on the outside.
So, for my primary needs I wanted: 1) comfort; 2) not cause sweat buildup, and 3) a solution for my bug. I bought the AG ShapeShift Modular Holster System with two shells (one for primary, one for bug) along with the ShapeShift Pocket Carry Expansion Pack. After a week of wearing IWB and pocket holster, I knew it fit my needs and I did not try the other type of holsters with the leather/Kydex designs. Thus, I would highly recommend the AG.
My SIL carries a primary and bug as well and he bought the exact same AG ShapeShift Modular Holster System with two shells (one for primary, one for bug) along with the ShapeShift Pocket Carry Expansion Pack and loves it. He carries IWB and pocket as well.
AlienGear has a 30 day trial period. Good luck with your search!