The 25-06 has several advantages, the ability to take 100 and 120gr bullets and drive them faster than the 6mm.

It is NOT a wildcat so that factory ammunition can easily be
obtained.

Being a necked 30-06 it would not have the feed issues
you'd expect of either a 250-3000Savage or a 220Swift
(you have to be attentive to how you stack 220swift shells in the magazine)

The 6mm-06 is simply too big to be "happy" as a 6mm
and it's a wildcat... though a kickass varmint cartridge

the 6.5-06 is not what I think of when I think "varmint cartridge" though it is a far better 120125gr bullet tosser than the 25-06 is the 25-06 can perform spectacularly with 75gr bullets...

a 25-06 loaded with 100gr controlled expansion bullets
(Nosler partition or Barnes TSX) will shoot as flat as you might wish the others will put a deer's lights out as well as you could ask for.

Just my opinion, I'm sure others will disagree.

AllanD

thanks I realy do like the barnes and want to try the tsx

I voted for the 6.5/06 as I like something different. The 25/06 makes more sense though as its factory available. In an M17 it'll be a heavy rifle, so should be okay for someone recoil conscious. If you've got a P14 (check your magazine length as I think they're shorter??), I'd consider a 303/25 as it'll match the 257Roberts in a mild package.
Cheers...
Con