I would shoot the 2506 before taking the 270 for Mule deer. The BC is better for the 2506 and energy is almost the same at 500yds.
What bullet are you using in the 25-06 with a higher BC than the 270? I wasn't aware of any hunting bullets with a BC better than .466 or whatever berger's 115 VLD is. Nosler 115 ballistic tip is a shade lower I think. I always liked the 25 but wished they offered a higher BC bullet like they do in 6mm or 6.5, maybe there is one I haven't heard about.
I am with you on liking the 6mm calibers, I shoot 100gr sierra gamekings from my 6mm Rem at 3150fps and have been real happy with them for coyotes. I'll probably take it on my next antelope hunt too, and my girlfriend will shoot it for deer. I've had real quick kills with the 6mm berger VLD bullets also, I got to test the new 87gr one for them. Neighbors took 3 deer with my rifle and handload and none went over 20ft. Internal damage was impressive and there was almost no external bleeding to contaminate a field with scent. I don't like the VLD's for coyotes, the delayed expansion doesn't do enough damage for me before passing through. Standard bullets open quicker on impact for the narrower chest cavity of yotes.
Sorry I kinda got off subject. I'm curious about the high BC 25 cal bullets though