There's super game improvement, game improvement, and various forms of player's club, generally forged.  At one end are muscle backs that are forged.  To simplify the discussion, I have seen Tom Watson's irons on various shows, and the wear spot is smaller than a quarter.  That accuracy will not result in fat/thin shots.  Which is good, because poorly hit balls will really be poor shots with the top forged irons.  Super game improvements have wide soles to aid in hitting by minimizing fat shots, with lots of vibration dampening so thin/skulled shots won't sting as much.  AP1 is a cast game improvement - doesn't have the wide sole of super GIs but does have a wider sweet spot on longer irons to keep mishits on track.  AP2 as a forged iron bridges from game improvement and the other forged irons.  Try getting a good fitter to work with your game.  Depending on your accuracy, that person will suggest AP1, AP2, or CB.  Likely they will suggest the AP!, based on what your level of commitment will be.  A couple of rounds a month and an occasional trip to a range means that hitting the ball straight consistently with some distance control is a reasonable goal.  AP1 will work well.  Moving to a forged set works for players that get to the point of needing to work cuts and draws.  Some game improvement products work so well at straightening mishits that working a draw or cut can be more difficult.  Another swing characteristic is launch angle.  Some of this can be controlled by the shaft, but CB and MB forged irons generally have a lower launch angle.

I agree with others that don't want to pigeon holed into a club based on generalities.  From your fitting, the fitter should be able to tell you what to expect with your current skill and you should decide to match your game that day or where you can see yourself.  I did flirt with a M53 forged iron.  I was hitting it ok, but my distance wasn't better than some older game improvements.  The AP1 gave me better launch and distance, I'm 62, and can't expect to get much better in 10 years.  Unless you can see a lot more time commitment, the AP1 will serve you well if they fit your swing today.

Thomas

First, "game improvement" and "players club" are labels, these labels DON'T mean "you stink" and "you be good".

The way you move to the next level is by moving to the next level of practice, the type of iron makes no difference.

Yes, there are advantages and disadvantages for every attribute found in clubhead design.

What I always thought was a great idea, was the progressive set, long irons had the highest degree of "game improvement" features with less in each shorter iron to PW having no "game improvement" features........now they are called mixed sets, where you take irons from different sets.

once someone gets good enough with the ap1s to be able to hit them consistently well, then they can move to the ap2s, a much more workable club than the ap1. with the ap1s, you sacrifice workability for forgiveness, while with the ap2s you sacrifice forgiveness for workability. The ap1s improve your game so you can get to the ap2s which are more of a players iron.

I'm 74 and over the years have gone from blades--Staff, Hogan Apex--to Titleist DCI Black and last year to AP2s.  The DCI Blacks were a great improvement over the blades in terms of forgiveness, but you gave up some distance and feel. I am very happy with the AP2s.   They have the great feel of forged irons, and are certainly more forgiving than the older blades.  I didn't try AP1s because I figure these may be the last irons I'll buy and I wanted to get back to forged clubs.  They simply feel so much better when you hit the ball somewhere near properly.