One big difference is the addition of a new four-model structure with Tour (T) Players (P) Extreme Forgiveness (XF) and Super Game Improvement (SGI) now offered. But the real design difference has to do with the a new material used in the clubs that produces more speed and distance among other things.
The most notable design feature of the new 0311 iron line is COR2 a proprietary polymer core material that’s 20% faster than the original filler material yielding more ball speed accuracy and consistency with the same outstanding feel PXG irons are known for. The new irons feature more of the material than in the past as well as an extremely thin maraging steel clubface improving performance across the board.
As is the case with all Srixon models the Soft Feel features an Energetic Gradient Growth Core that produces low spin and high launch for outstanding distance. The Ionomer cover on the new Soft Feel is softer and thinner than in the previous model allowing for improved spin rates on short shots around the green as well as an overall more pleasing short-game feel.