Up here in the Pacific Northwest, I’ve seen a little trend away from the little 6mm’s, myself included. We get some decent winds and weather for a lot of matches. Lots of guys shooting the 25 creed and a few went back to the 6.5 creed. The 25 creed cheats wind better than the smaller 6’s, only marginally more recoil, good barrel life, and better splash to pickup for corrections. Plenty of top shooters shooting the 6.5 Creed with the 140, 144, and 147’s. I ran a 6 BRA for about a year… fair weather is was fine. Wind and rain made things challenging, especially spotting misses in wet earth with little 105 gr slugs.
The 6 ARC leaves a little in the table for PRS I think. Between the cartridges you mentioned, I’d go 6.5 CM, but don’t hesitate to take a look at the 25.