I just went through the purchasing process for a new set of irons and I will try to outline my thoughts on the different Irons I hit. From the clubs you mentioned, I think the MP59s are probably more closely related to the AP1s. The AP2s are not very forgiving whereas the AP1s will help in that area a little more while still giving control.
The different clubs I hit included AP2, AP1, MP64, Cobra (Amp Pro?) and Callaway X forged.
AP2: Coming from the 2008-9 model of AP2 irons I wanted to test out the latest model. To me nothing really changed from the irons I had to what I hit. They are solid irons but not as forgiving as what I wanted (why I decided to switch from my AP2s). The feel is the feel you get from a forged club, but nothing special in my opinion.
AP1: I liked the AP1s, but the Golfsmith store I was at didn't have a full fitting cart from Titleist yet so I didn't go any further than the demo 6iron they had. The shaft combo was not the best fit for me so the results were mixed. Again the feel with these were alright, but nothing special.
Cobra Amp Pro: I really liked this offering from Cobra. The demo 6 iron I hit felt really nice and results were fairly consistent. The feel was very good, probably a little better than the AP1/2 and in line with the Callaways that I hit.
Callaway X Forged: I have never been a Callaway fan. I started playing with a set of X14 steelheads back in high school so I decided to give them a shot. The ball definitely feels good when struck well and the club looks great at address. My results with the irons were not as good as the cobras or the mizunos.
Mizuno MP64: After 1 hit with these irons I understood what the big fuss about Mizuno's grain flow forging process is all about. When struck well you don't even feel the ball coming off the irons. A slight mishit is noticeable once hit; however, they are still forgiving enough that you aren't punished too much. At address these irons look nice, probably not as nice as the Callaways, but a very close 2nd. The overall look of these clubs are very nice, nothing extravagant just a solid design. One thing I liked about the Mizunos and the others might have done this as well and I just didn't notice, but the cavity decreases as you approach the PW. This allows for more forgiveness with your long irons and more control of shot shape with your short irons.
I ended up ordering a custom fitted set of MP64s