The metal in cheap chains of any kind, including Izumi, will wear quickly and allow the appearance of stretch. The only Izumi chain to consider is really the Izumi V. It's high grade steel, much better pins, and the rollers are hard tempered steel. I monitor wear and I am on my third year on an izumi V on the track. Especially with track mileage, it's a chain that tends to last forever. You just can't cheapen out and buy the lower grade versions within the brand.
As for six-day riders riding 3/32, there's a feeling among pro six day riders that the 3/32 chain is simply smoother. You're riding pro six-days (at least in the long chases of the madison sessions) in low gears like an 88 or 89 at very high cadences like 145 or so. Anything that makes a rider feel he's got a little more leg speed will sell.
As for what you're going to put on your bike, a 3/32 drive will last pretty well as long as you use real 3/32 equipment and not modern 11-speed chainrings and chains. The only drawback is that you have to keep the chain tensioned without too much slack because the 3/32 chain will definitely try to derail more easily than a 1/8 track chain will do -- it's designed to derail, if you think about it. And before someone asks, hipster poseurs like to tension their chain out so you can almost pluck it. The theory is that it helps with track stands but mostly it's just ignorance. Good track mechanics leave about 3/4" to 1" of vertical slack in the chain as a conservative rule, and many riders like a lot more than that. As long as you can't take a wrench and push your chain off the chainring as you turn the cranks, you're ok. The looser chain is easier on the chain, easier on the whole drivetrain, and your legs take much less of a beating if they have some slack in the chain.