I started out exclusively with Lee 4-die sets, which included the FCD (.45 ACP, .40 S&W, .380 ACP), and it is easier to seat and crimp separately, especially when starting out. I started on a turret as well.
When I upgraded to a progressive, I began changing out my dies, since the Lee dies are a little short for the thicker progressive die plate.
My personal opinion is that it's easier to start with the Lee dies, and use the FCD. However, if you want to seat and crimp in the same stage, I found it easier to do so with the Hornady dies.