Using 3G/4G vs. 4G LTE
Does using 3G or 4G instead of 4G LTE on my iPhone (AT&T) conserve data consumption on my limited data plan and does it also conserve battery life?
Data consumption should be the same. Battery consumption with LTE will be higher than 3G/4G especially in areas with weak LTE signals.
See this article for some detail: iPhone 5 Battery Life Reduced Due to LTE Signal Strength