I'm a little bias against the flighted shafts.  Essentially the flighted shafts have softer long irons to promote higher flight and stiffer short irons to promote lower flight.  In my mind, the club face affects trajectory more than shaft.  Essentially you have a set of unique shafts that feel different versus a set of consistent shafts that feel the same. If fitted for the regular 5.5 shafts, go with them.

RC

I play the AP2 710 w/project X 5.0 shafts. I am considering the 712 w/ KBS reg shafts. My question is will the these shafts play similar to the project X 5.0 or should I stay with the 5.0's which I really like?

As a matter of fact, I have 712 AP2's with KBS Reg. I usually try to wait before I take them apart, but I can't help myself for more that a week. I pull the heads, spine the shafts and remove those annoying tip weights. I'd rather have lead tape on the head than weight in the shaft tip. When I pull them I'll put in a few different shafts and go to the range, then the course and finally the launch monitor.

 KBS and PX are a very different feel. KBS shafts are the best freq matched shafts I have ever seen. PX were great before TT took over the production. I would say that from purely a shaft flex perspective that the Project X 5.0 will flex like KBS R+ or about a 5.5 rifle flex. Soft stepping the PX once or twice will get you closer in flex to the KBS Reg, but again very different shafts. Another option to try in that range would be the Dynamic Gold SL R300. Suppose to launch low but it doesn't in the AP2 712. May end up in mine!

 If you like what you have stay with it. Go get Fit with trackman and try everything! Ignore preconceptions of what you have read or what you think is cool. Then  talk the fitter into letting you take a few irons to the course. Hit a few balls in from your distance (ie 6 iron if that's what iron you have). How do they launch? How far do they travel? Most important , how far do they roll out when they land. On the course is when it matters. If they are easy to hit and do what you want them to do.......... Don't ever change them!!