Ive played both with same shaft. IMO 712 are easier to hit and have a bigger sweet spot. They go higher too. I like them better than ap2's. Awesome feel and workability

I just changed from AP2 to 712 CB.  Plenty forgiving and much better ball flight.

I've gamed them both as well and I agree with Kurt. Plus the satin finish is beautiful. Great irons

I'll second that as well. I have hit both and not only do I feel the 712's are easier to hit, they look stellar! I like them much better than my Ap2's I used to hit and feel much more confident striking the ball. I'm probably getting better with playing more but I still love hitting this club and feel most people would also prefer it over AP2 if they gave it a try, just my thoughts. 

But to answer your question, maybe not a huge difference between them but enough I felt it was worth the jump, that's my excuse anyways:)

TGW