I started sorting brass back when I was shooting Bullseye matches in the 1970s, so it was easier to know which was mine. Of course, now, only a few guys shoot .38 Specials in the Centerfire match, so it's not as important. But, oddly enough, the other day at the Dallas match, I had a guy shooting a Model 52 next to me and another guy with a Clark down a few positions. Luckily I keep a Sharpie in my gun box for just such an occasion. The brass catcher doesn't always get them all, but it helps.
I do feel a little more confident in their consistency when I use the same mfg, especially for match loads versus practice.
I know what you mean about the powder slides. I had one that was supposed to throw 3.0 grains of BE. When I checked it, it was only throwing 2.7. I used a fine swiss file to open it up a little, so now it throws right around 2.95; close enough. I do have a couple of the adjustable slides since I have a separate press for .38s and another for .45 ACPs.
I had to go to a 7 pound recoil spring in the Clark to get it to function with the 2.7 load. I'm not sure what weight the original spring was, since it had been cut down from a heavier spring. I had Clark build it in 1982. I did have a new bushing put in a few years ago when I noticed the groups opening up and I had the slide tightened. We have a good local gunsmith who works on 1911s. He built my Hardball gun for me that I used to get my Distinguished Pistol medal.