Can’t really give you a technical reason because the playability factors are basically the same. 12 point difference is not noticeable. Other than the fact that you deserve a new set of clubs after playing a set for 10 years, I doubt you would see much of a performance difference just based on the head design. Of course the M890 is a wonderful, ultra playable design, but the 2011 Razr was as well. The M890 has a higher MOI, and that probably accounts for the slightly higher playability. This comes from the longer blade length resulting in a longer c-dimension, translating into stability and a high degree of forgiveness. Lofts on the two are within 1/2 a degree, so no advantage or disadvantage there. The M890 has a wider sole, so it may be a little more turf forgiving. One of the reasons, I suspect, that you played the Razr irons so long is that they were so playable and forgiving. There haven’t been may irons developed since 2011 with Playability Factors in the high 900’s. Sticking with that kind of playability, no matter what model you choose, should give you another 10 years of good performance.