I'll echo other Crossbreed recommendations. They have been the most comfortable design I've tried so far. Over time the leather backer will mold itself to your body making it even more comfortable.
I've tried alien gears shapeshifter and it's really nice. The soft backer does a fantastic job bringing the gun in tight without being so rigid it creates hot spots when sitting or bending. It reminds me a lot of the older milt sparks Vm2 I wore for years but with a more positive click-in type retention.