Both of the cartridges you are considering, the 25-06 & 270Win., would be excellent choices for pronghorn and mule deer, as well as those whitetails you currently hunt.
Personally, I'd pick the 270Win. I think it's more versatile, with the heavier bullet weights available. And, given past experience, I can't tell the difference in recoil levels between rifles of equal design/weight (117/120gr. vs. 130gr. in 270). I think too, the
270Win. will give you a better/wider selection of ammo to choose from.

ps: keep the 243Win. for varmints