CCI manufactures the Hornady, CCI, and Federal brands.
Eley makes the Eley and Remington brands.
Eley has shot best in my 17 Mach 2. However, I would stay away from the Remington. A recent batch I bought from Natchez had a high % of bullets in each box that had crooked or chipped tips, bad crimps, or nicks in the jackets. Seems like Eley was packaging the Remington like "seconds."
YMMV.
Many people say there are differences between the CCI and Hornady. I fully acknowledge that one batch of ammo may be better than another--based on how the production machinery was spec'd at the time of that particular run. But you can't really say that Hornady is better than CCI is better than Federal, etc. ... because those three brands all use the same powder, cases, and bullets, and are produced on the same machines.
It's sort of luck of the draw unless you can identify particular lots. With the Eley, it seems like the earlier the better.
I may end up having mye 17 Mach 2 rechambered to a 17 Aguila. The reason is that the Aguila uses the 20gr CCI bullet which seems to be more accurate, and the bullet is seated longer so you can cut a chamber to get the bullet into the rifling.
In upper right, 17 Aguila on left and 17 Mach2 on right.
But the 17 Mach 2 goes faster--2050 fps vs 1780 for the Aguila.