Sight unseen, that's a tough question.  First, we would recommend going to a fitter to hit both the AP2's and the CB's to see which might suit you better.  If you go to www.fittingworks.com,  you can put in your zipcode and find both Fitting Days and Fitters in your area.

Starting from the assumption that you are looking for a club that is more workable and less offset than your AP1's.  The CB's work for the player that is looking for more forgiveness than the MB's provide.  They are the cavity back companion to the muscle backs.  Players that liked the ZB's or the 735's and want to move into new sets will find the CB's a good update.  The AP2's are the forged version of the AP family.  They are more forgiving and a little more offset than the CB's and will also hit the ball higher.  The progression of the three models in terms of forgiveness and workability from most forgiving to least would be AP1's, AP2', then the CB's.  There are many variables that go into selecting an iron that would work best for you.  I would check with your local pro to see what he/she would recommend or give us a call and we can find a fitter for you.