All depends on your intended use.
If you want total versatility and you have the rifles for it then the four die set is a good idea.
But you will not use all four dies for every rifle load that you create.
For an AR platform I full length size and decap, then seat, then crimp in a separate operation. You can seat and crimp in one step, I have just had better results in a progressive operation doing it separately.
As noted above there is no benefit to using a neck collet on for example a 5.56 chamber.
But if you have a tight target chamber in one of your bolt or single shot rifles and you want to dial in for some very precise loads you may wish to use a die with a neck sizing collet to get exactly where you want.
I have only had a couple of rifles where the chamber dimensions let me use a neck sizing collet for a particular result. Unless you do have this situation just get the three die set. As noted by another poster above you could get by with just a two die set but since you have a turret why not take advantage of the stations?