Have never used anything but a belt clip IWB holster with the clip having a "J" hook at the bottom to make sure it can't pull up/out. Shove it in your wasitband in 10 seconds and you're G2G. All the extra stiff leather and snaps to hold the gun on the belt have unwanted side effects, and they are comfort and concealability. The comfort is pretty self-explanatory, and the concealability is best explained with one photo:
This is a SAR K2 45 with 15 rounds of 45 ACP ammo in it, and the holster is a soft leather one weighing maybe 3 ounces and having the necessary J hook on the clip.
In place, the gun mooshes into my aging 800 lb. troll love handles, and it's damn near invisible under a t-shirt. This is the exact opposite of a mini .380 or 9mm autoloader with 15 rounds of 45 ACP ammo in it, and there's just nothing you can see from the outside.