"Standard 4G" is kind of a meaningless phrase. According to this article, disabling "LTE" means it's limited to either CDMA 3G or HSPA+. HSPA+ is supposed to have performance comparable to LTE, so I would guess that if you disable LTE and see a "4G" icon, it means you're getting HSPA+.
PC Mag confirms that Apple (like their competitors and partners) started using "4G" to refer to any post-3G network, like LTE, WiMAX, and HSPA+.
Anyway, most of the articles I've found comparing power usage between HSPA+ and LTE suggest that LTE has slightly lower power consumption, but it seems to be a pretty small difference. The signal strength where you are located probably has more impact than this setting. Early LTE phones apparently sucked a lot of power even when idle, but with newer phones this seems to have been improved, e.g., this iPhone 5 user claims battery life is "nearly identical" whether LTE is enabled or not.
So you can try both settings and see which works better for you, but I wouldn't expect a huge power savings.