There is a great article by Chuck Hawks at the following site:
http://www.chuckhawks.com/rifle_killing_power.htm
Even if you don't agree on some of his comments, it is a terrific accumulation of knowledge and is very thought provoking.
On a personal note, I have been shooting a 25-06 for the past 29 years. It has killed more deer than I can count. I have killed a couple of deer and an elk with a .270. So either one will get the job done. It's all about the skill of the shooter and most importantly - SHOT PLACEMENT!
Good luck on your selection,
SD Shooter