Conditions, and hunting/shooting skills play important roles here, too. I know of several hunters who routinely take deer (cleanly, I might add) in the Central Texas Hill Country using .222's or 220's. They have been doing this for many years, and rarely - if ever - lose deer, or have to make follow-up shots. Of course, they are hunting from box blinds and rarely take shots greater than 40 yards. Also, head shots and neck shots are the rule. Some of these folks don't see any need whatsoever to shoot larger calibers. And, while I personally prefer larger calibers, I would never argue with the successes that these guys have had.
Also, they have pointed out to me that many hunters who hunt heavily wooded areas, such as in the upper midwestern or the northeastern U.S., and who often take running shots at deer, are proud of putting several rounds into the animal to stop it. They have asked me which I believe is the most humane -- "small caliber/close shot/one shot" or "large caliber/running shot/multiple shots?"
Usually, I just shrug my shoulders and try to change the subject!
Regards,
jbgood