I recently started carrying a TLR-1 on my EDC pistol and had some trouble finding a IWB holster. I have been doing IWB since I got my CCW license 5 years ago. I ended up purchasing a Crossbreed Light Defender series holster that cost me $125 with rush processing.
I also wanted to update my OWB holster used for 3 gun to one that would hold the light, so I purchased a Bravo Concelment BCA light bearing OWB kydex holster with the intention of only using it for matches. Well just for giggles I put my OWB holster on my normal clothes, wore it out into town one day and instantly fell in love with OWB carry. I had my IWB holster for about 2 weeks before i made the switch.
Here are some things I am noticing about OWB carry -
Advantages over IWB:
Your belt stays on your hips better - My IWB holster was always moving even with good gun belts so I was constantly pulling my pants up. Just having the flat leather IWB inside your belt "shimmed" the curve of your hip and makes it slip more than OWB. With OWB it hardly moves and even if if does, we are talking maybe a quarter inch.
It doesn't wear a hole in my pants - All of my pants eventually get a hole in them where the muzzle end of the pistol is with IWB.
I don't need bigger pants - this makes me not look like MC Hammer because I can buy pants my normal size.
Disadvantages over IWB:
Prints more - because the gun is not a tightly snug against you it will print a little more. I have, however, started to care less about printing in the last year as I have realized that most people are so wrapped up in their own business that they wouldn't even noticed if I was open carrying.
Your holster gets exposed more. Some of my opinion in the previous point applies, but I am also compensating by being more aware of who is around if I have to reach to the top shelf in the store. It is also a concern when sitting as your shirt can ride up so I need to be more conscious when sitting.