I like the 25-06 and use to use it a lot in the 1990’s when I did quite a lot of hind culling on an estate up North. I used an estate rifle - a Sako TRGS in 25-06 fitted with a fixed 10x42 Scope. I never even considered range or bullet drop. It was either far too far or just shoot it.
I did consider getting a 25-06 at one point, but by that stage most of my stalking was Roe deer on central
Scotland farmland and the 25-06 was just a bit too fast and messy for 100m ranges I was shooting.
The 25-06 is possibly lacking a bit in bullet weight for big red stags. Old lead cored bullets, high velocities and big tough animals don’t usually equal good results. But these days of monolithics, smaller bullets at higher velocities work well.
25-06 win by using lots of velocity to make them very flat shooting.
The 6.5 CM uses a long ballistically efficient bullet that maintains energy long way off. But it still has quite a curvy trajectory so do need consider ranges inside 300m. On targets doesn’t matter. You can adjust to the range then shoot.
25-06 just point and shoot and its flat for any sensible stalking range.
Better or worse than a 270. I doubt you would notice much difference in real life. 25-06 is really a big powerful little cartridge. Certainly bigger and more and authority than the 243, the 25-06 is probably the biggest dual purpose vermin / predator and deer cartridge, whereas the 270 is really the bottom end of proper big game cartridges. You could take a 25-06 to Africa and shoot a Kudu or Zebra and probably get away with it. But a 270 - used all the time.
25-06 has never been popular and has generally been a reloader’s cartridge, whereas the 243, 270 and 308 you can find ammo and bullets anywhere.
25-06 and 6.5s - there is not really a fair comparison as historically the likes of the 6.5x55 shot long heavy for calibre bullets (140 to 156gn )at moderate velocity of c 2650 to 2700 fps, mimicked by the 6.5 CM, 260 etc. The 26-06 shoots 115gn bullet at well over 3,000 fps. There is the 6.5 -06 but that is AKAIK just a wild cat. The 6.5 PRC is probably a fairer comparison.