OWB is more comfortable even though I hated it when I was in service.
IWB can be nearly as comfortable as OWB, it takes the right gear and gun, hence you may spend some money for holsters and probably get another gun as well.
There has to be a level of movement in the gun and holster setup or elsewise your belt will be too tight and that can be very uncomfortable, especially over a prolonged period of time.
I ended up with a relative light gun and two different holsters, a kydex holster and a dual carry which can be converted to OWB in the same riding position as for the IWB setup. I use the kydex holster for in and out as well as short trips leaving home. For longer trips I use the dual carry either way.
The good part is just the fact I never had to draw my gun other than at the range or for exercise.
