I chose the Recoil shafts because UST is claiming that they have all the benefits of graphite and steel in one shaft, and what little I've heard about the Recoils from independent 3rd parties has been very positive. Additionally, I've heard Kuchar and Snedeker are using them now on tour. Finally, when I bought my first set of irons, I was fortunate enough to not know that I was supposed to prefer steel shafts "because that's what the pros play", so I bought graphite and never suffered severe vibrations on mis-hits while I was learning. Subsequently, I grew to love graphite shafts and the Recoils appear to be, at this time, the closest to the ultimate evolution of that technology.
I am interested in hearing why some people want heavy shafts. I don't see any advantage to heavy shafts, and if it's just because heavy shafts feel like steel, I can do without that.