308 is better it is a higher caliber and shoots farther unless you want a cheap gun 308s are more expensive making you want to choose a sucky brand 308 which makes the 270 better.
It all depends on what you are hunting.
The .308 has a shorter cartridge case, and a fatter bullet. The .270 is based on the 30-06 case, about a quarter inch longer than the .308 case.
Depends on your definition of better. All 3 are capable of taking any game found in North America. The 8mm Mauser carries a little more energy than the .308. The .308 may have an edge in accuracy. The .270 is basically the 30-06 necked down to .27 caliber, shoots flatter, due to higher velocity. This is one of those Ford/ Chevy/ Dodge discussions.
Either can depending on the load
Angels dancing on a pin. Either will get the job done.
270 are better
Long action. The .270 cartridge was based on the 30-06, a long action. .308 length is short action.
Main one is bore diameter. Another answer: 270=.277 diameter 30-06=.308 diameter
The parent case of the .270 is the .30-06, necked down. The parent case of the .243 is the .308 Winchester, necked down. Aside from the larger diameter of the .270, the .270 has a longer case.
General rule of thumb is that the best caliber is the one which best suits you. Of the two, .270 would be the more powerful round. Both are substantial for hunting something like deer, although the .243 is probably better suited for the experienced hunter, whereas the .270 would be a little more forgiving to the novice hunter. The .270 is a necked down .30-06, and the .243 is a necked down .308.
In my opinion theyre fairly close to each other. Theyre both based on the 30-06 cartridge case. The 270 shoots lighter bullets at higher velocities but the 308 can shoot heavier bullets. I would base a choice depending on the application.