2nd type is more for competition; essentially zero retention if doing anything other than standing up right, and you need to practice holding/loading w/ 5 shells in your hand.

Personally, I prefer the 3rd type. I have a vest that's set up with (2) Blackhawk! vertical pouches that hold 18 rounds each : http://amzn.com/B001QGLSSU .

This new set up I have on a modular vest is AMAZING; shells are secured and very smooth to load strong hand (which is what it is initially set up for), or off hand as well. And the fact that I have 32 shot shell sin just (2) pouches is worth it on its own. The major downside, of course, is that you have to load the shells one at a time; but with practice, I can see someone pulling out X amount of shells and loading them as quickly as a speed loader.

I'll take a pic when I get the chance 

I just use the bandolier as a belt. Only problem is that most shot shell bandoliers make crappy pistol belts, so you gotta make do with what you got. Until I can figure out a way to sew my own shell holders onto a pistol belt, I'm willing to sacrifice the extra shells.