That’s a hard one for me.
I have several .308 cal rifles, 30-06, 308 Win, 303 Brit (though thats .311-.312) and 300 BLK. I also own a set of swaging dies for .308 Cal bullets, and of course all the dies and reloading equipment for each.
I am always hesitant to get a new caliber, but I have done along shooting and load development for 6.5 Creed and I think it’s an excellent cartridge.
I don’t think there’s a wrong answer here, you can just about do everything with a 6.5 that you can do with a .308 Win or 30-06. With a little less recoil.
Pair a 140 Matchburner with RL16 and you have a top notch target round. A Barnes 129gr TTSX coupled with RL16 will take just about any deer sized game out there. If you do your part I am sure Elk and Moose aren’t out of the question.
If I was to advise a customer, I think I would point them towards the 6.5 over the .308 simply because I know they will likely spend more time shooting due to the reduced recoil, and muzzle blast. However I would caution them that 6.5 is widely available but not as available as 308 Win. So store bought ammo may be a bit more expensive but a reloader wouldn’t care.
As far as the higher BC and the benefits there...eh, I think there it validity to it but I think sometimes that is overhyped. Proper bullet selection and you can get very similar ballistics out of both.
Reloading...it’s like knitting for men.