Here is my take on belts. I used to think that the more stiff the belt the better and that may be the case for some. But after I switch to AIWB I could not get a comfortable ride with my stiff Volund Gearworks belt. Tom suggested I use a less stiff belt and see how that worked for me. I first used a thick leather belt that I had and comfort was better but not great. I then switched to my flimsy Dickies belt and WHAMMO!....comfort. So I have been rocking this crappy belt ever since and all has been well for me with AIWB carry.
This is what I think is going on.
https://dl.dropboxusercontent.com/u/...iff%20Belt.png
For me, my belt always rides lower in the front than in the back. Add a gun in there and the front will sag a little more. A stiff belt will not conform to that shape very well. It wants to keep its form and as it sags in the front it actually forces the muzzle end of the holster into my body causing discomfort. It also makes the rear of the slide print. Basically the stiff belt forces the holster to tip out.
https://dl.dropboxusercontent.com/u/...ble%20Belt.jpg
A soft belt will more easily conform to my body and the holster. This will pull the holster in tight to the body but not force the muzzle end in. I'm sure my Dickies belt will not hold up nearly as well as a nylon belt but for now I am sticking with this belt because I get much better AIWB comfort. I have heard good things about the Volund ATLAS SLIM belt. When my Dickies belt craps out I will probably go for the Volund SLIM.