This is just my 2 cents... Steels the deal! Most of your irons are shafted with steel, you are going after a specific distance and a controlled shot. graphite shafts are meant to generate as much clubhead speed to "mashed potatoes" a golf ball! When swinging a hybrid, if your replacing a 2, 3 or 4 iron, your probably going after a specific distance, not like a driver. So my opinion is steel is the deal! I personally have a 2 hybrid, Nike Vr Pro shafted in the Dynamic Gold SL S300, my irons are Nike Vr Pro blades shafted in the Dynamic Gold S300, the shaft in my hybrid plays very similar to my iron shafts and is lighter to keep the swingweight down, but with this said, I am a longer striker of the ball and distance doesn't phase me, I'm after controlled distance and most imortantly shot placement. Maybe if your not a long hitter the graphite will benefit you more... this is just my 2 cents and hopefully it helps you out some!
