I really like 25 cal cartridges, but it is more of an emotional affinity based on nostalgia for the 25-06 more than anything.
But looking at the numbers, nerding out on the minutia, I just don’t see any practical (for me) reason to switch from the 6.5 to the 25.
Having used a 16” suppressed 6.5 with 130 TMK’s for two seasons now (with one more hunt left this season), there is zero value in changing. I do think the capacity of the CM case shines in the 130ish range - I understand that many use the 147, but in my application the velocity is just too low and recoil goes up.
My 130TMK load is 2750. I would lose velocity going to a 25 cal 134; I would gain BC but for a 500 yard and in application (how I hunt) that benefit is essentially moot. While having essentially the same recoil.
My point is, I think the 25CM does offer some objective advantages to the 6.5CM IF comparing certain bullets launched from certain barrel lengths to achieve certain velocities. The question then becomes, are those advantages, albeit small, pertinent to you, your envisioned rifle system, and your style of hunting?
For example, in the Hornady Podcast comparing all the Creeds, Jayden said the 25CM 134 provides 4” less drift at 1000 yards compared to the 147 6.5.
Again, is this a practical advantage for you?
Maybe. Maybe not. For my use case, no.
I do see however, an advantage to the 6CM with 108/9s: higher velocity, with less recoil than my current set up. 22 CM makes the most sense to me, but I hunt CO so that’s a non-starter.
That said, I will likely still a 25CM simply because I have a ton of 25 cal bullets sitting on the shelf. However they are “old school” in the 100-110gr range. I could do the 25CM in a 16” barrel set up shooting these bullets for the wife to achieve less recoil than my 6.5 set up; with her shots should be no more than 300 yards. My concern however, is accidentally mixing up the cartridges in the field: imagine two identical tikka mags, both loaded with green tipped Sierras… I can see an accident happening.