Eddie, the advantage of the micrometer pistol insert that fits the rifle drum is no drum changes and lower cost for the same result. The insert fills most of the rifle drum opening and has a small diameter rod that adjusts inside the middle resulting in a smaller cavity appropriate for pistol measurements. Pricing and pictures are from Midway.
Here is the micrometer rifle insert: ($25)
Here is the micrometer pistol insert (being discontinued): ($25)
Both of these use the rifle drum (and a Big Brown Truck will be dropping off one of each at my house tonight).
Here is the replacement pistol drum with a basic (non-micrometer) pistol insert: ($26)
You cannot buy the basic pistol insert by itself, only with the drum.
Here is the micrometer pistol insert to fit the pistol drum (only): ($25)
In the near future, it'll cost $26+$25= $51 to get micrometer pistol adjustments vs. $25 for the one that fits in a rifle drum (while there is still stock available). Both create the same size (diameter) cavity for measuring pistol powder.
When first setting up the press with a dillon crimp die in station #5, I almost cut the ejector wire into 3 pieces before I discovered why my crimps weren't getting any better but the press was getting harder to operate.... Dillon crimp dies have a radiused opening that is fairly sharp on the edges. I bought Lee taper crimp dies then got out the hacksaw and grinder to make them work in station 5. Hornady replaced the ejector wire when they replaced the shellplate.