Because all auto loading rifles should always have the brass full length sized, you will be buying a neck sizing die you should not be using. Unless you also have a bolt action rifle the 3 die set would be better/ less $.
I full length resize all of my brass and then run the brass through a neck sizer. I reload for 7 rifles including a bolt action. I have found this eliminates any mistakes and I can run the ammo through any of the 7 rifles without issues. I use a Lee 4 hole turret press
kwg