Semi auto pistol ammo seldom "looks crimped." The taper crimp on this ammo just removes any excess flare (if any). The only rounds that you make that should have a visible crimp should be the rare cases that were the longest on the bell curve. Well, there's a school of reloaders that like to put a visible tapered crimp on the case mouth using Redding crimp dies. But that's a different story.
Factory rifle ammo should only look crimped if the bullet has a cannelure. Then you'll see just a slight bevel/indent at the end of the case mouth.
If you want to make sure your pistol ammo works reliably in most all guns, you should crimp it. Average brass thickness at the mouth is 0.01". If your case mouth measures no more than 0.02" larger than the diameter of the bullet, it should fit in any chamber. If you don't crimp, the best you can probably do with mixed brass will probably be around 0.04".
If your guns have generous chambers at the case mouth and you don't overdo it when you flare the cases, you'll find no need to crimp. But some day you might buy a new gun and find it doesn't like your reloads.
For small bore rifle, it's different. You don't flare the case mouths. So you don't need to crimp, unless you have a specific reason for doing so.
For pistol ammo, I use the seater die to crimp. If you're using cast or oversize plated bullets, or if you're using thick brass, the FCD can damage the bullet and reduce neck tension.
For rifle, you obviously would use the FCD, since that's the only way to do it.
