Coincidently I have been working on the same stuff. I have a few brands of brass. I have Winchester that I bought new. I also have Herters, Frontier,Hornady), WW Super, Super-X, and Lapua. I had others but scrapped it. When I got the idea to try to trim the necks I decided on the K&M neck trimmer. I was in the process of buying it and while talking to the retailer I mentioned that I was shooting a 222. He said really, well I have some Lapua brass on the shelf. I asked how much he had. 200 rounds was the reply. I bought it all. That was good fortune for me. If you are buying from a retailer I would suggest that if you want the Lapua brass, that you give it shot and ask. Anyway I measured the brass and began learning how to use the trimmer. I started with the Frontier brass. Here are my notes on the brass that I have.
RWS - No experience
FC - had some, scrapped it all, don't remember why
R-P - don't remember having any
Herter's - NLA new, fairly nice brass, small flash hole, necks are on the thin side but fairly uniform
Super-X - thickest necks I have found so far, will neck trim to .013 min. No longer in production.
WW Super - current production, maybe the best readily available and economical, fairly thick necks with average uniformity
Frontier - very deep primer pockets, did not clean up well, necks have quite poor uniformity and are of medium thickness
Lapua - standard size primer hole, some are not so uniform, necks are the most uniform of this list, currently unavailable unless you are lucky and find some NOS
For those of us with factory rifles with .253, or actually .255 - .256 chambers, I would think it is most logical to use the best brass with the thickest necks and bullets that have the largest OD and a flat base. For me this means WW Super brass with Sierra 53 gr #1400 bullets. If I have any luck and decide to trim the brass, I would try to remove ony enough to even up the necks which will still have some portion unturned. The closer to .013 the better. Good luck, Peter.