IWB:
Better concealment - Check
More secure - Check
More comfortable - Check!

Once you get used to IWB, there is no other option. I tried OWB recently with a quality holster and a good belt and didn't like it at all. As others said I just felt like the gun was not secure to me.

IWB for me with a 1911, no questions asked.

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Still carrying my S&W 642