I didn't really know which forum to put this in, so I settled for this one because it's the one most people seem to read consistently.
I am planning to put together an AR upper in one of the "thumper" calibers for hunting with a silencer. That means subsonic ammo. I had just about settled on the 458 SOCOM (which uses .458 bullets like a 45-70) simply because Starline makes brass. Another option opened up yesterday when I found out they are also now making brass for 450 Bushmaster, which uses .452 bullets like 45 Colt and 45 acp.
I have molds in both diameters, up to 500 grains for the SOCOM and up to 300 grains for the Colt. So I don't need to decide based on bullet diameter. All things considered, is there any particular reason to choose one cartridge over the other?