If this helps, Titleist irons have been the number one irons played week in and week out on the PGA tour (minus maybe 3-4 weeks) since 2007 when the AP family was introduced.  AP2 irons are played by between 1/3 and 1/2 of those players.  This year approximately 28% of players using Titleist irons are playing AP2 irons, 27% are using the CB's, 40% are using the MB's and 5% are using AP1's and other Titleist irons.

Thanks for the insight.  Based upon these statistics, is it fair to suggest the AP2s and CBs are closely aligned, as it related to look, feel, and playability?  In comparing the two models, what is feedback provided by the tour players?

Can't we say both?

Hm.  Maybe I should have provided a fourth option:

Game Improving Player 

The impression I get from Titleist's ads and the reviews in the usual monthly magazines is that the AP2 is  enough of a players iron, but has a lot of game helping weight manipulation in it, (behind the back plates), so it's a really good combination of both categories.

Both... depends on the player.