When to progress to blades/forged/tour irons??

Sounds more like a problem with the player than the equipment. If you can't hit a straight high shot with a blade, you can't hit one with an AP2 either.

Zach does indeed use APs (although only 1 of them is an AP1), but then they are the bigger sellers in the Titleist range and Titleist encourage their staffers to play them.

Lets examine a slightly bigger data set. Say last 10 years of Open Champions. Last year's winner, Rory, uses blades, as did Phil Mick in 2013, the one from the year before that, Ernie Els, and the year before that, Darren Clarke. OK, the year before that, Louis Oosthuizen used Ping S57, those are pretty blades but have a small cavity. Anyway, on to 2009, Stewart Cibk, yep, blades, 2008 and 2007, Paddy H used cavity back pPi7s. 2006, Tiger, blades.

So, what was the point exactly?