I find my procedure is dependent on the boolit and gun combination. Some applications require the two die technique, and others don't. Back when I liked to use a 3 hole turret press, I'd seat/crimp in same step when ever I could. Now that I sold the 3 holer and use a 4 holer exclusively I always seat and crimp is separate steps. I load for both revolver and semi-auto. Lee's taper crimp has become a good friend of mine. Even still, my Semi auto won't cycle a lightweight SWC, which bums me out. My revolver has issues with fat RN boolits, but I am not a fan of them anyway. So, there are reasons for everything.