If you are a handloader,it's a toss up. If you rely on factory ammo,the 270 just about chooses itself.
I have both,have killed stuff with both,like both,the 7x57 prolly is a touch more pleasant to shoot with any given bullet weight because it uses less powder and generally operates at lower pressures. That is why the late Jack OConnor selected a 7x57 for his wife to use as her primary big game rifle.
For practicality go with the 270.
For user friendly style and class get her the 7mm Mauser.
