For me it's all 3.

Conceals better. Since most of the gun is hidden inside my pants and I don't need longer shirts

More secure because it's being held between my body and the belt. OWB holsters pull down more than iwb for me. Even with a good belt.

Very comfortable for me. Most times I forget I even have a gun on me. When I remember I often grab for the spot to make sure I haven't accidentally lost it
Im actually a little paranoid that if something were to happen to me I'd forget that Im even wearing a gun.

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