The adoption of IoT use cases across a broad spectrum of application areas has increased manifold over recent years, with energy efficient low power wide area network technologies gaining significant traction. Due to the existing infrastructure of widely available mobile networks that covers a majority of the globe, these networks provide a platform for IoT deployments at scale. In order to be able to fulfill the energy requirements of many IoT use cases, efficient radio access technologies like NB-IoT and LTE-M are supported by a growing number of operators. However, a detailed understanding of the impact of these access technologies on both the energy efficiency and quality of service of IoT use cases is largely missing today. To this end, we perform a detailed measurement study, evaluating the impact of both radio access technologies on the energy consumption of end devices. We investigate further which radio technology is best suited for what type of use case using different application protocols, namely MQTT and HTTP. Our measurements show that NB-IoT is best suited for longer idle durations, while LTE-M should be used for more active devices or if larger transmissions are required.