The consolidation of services is a widely accepted technique for IaaS Cloud providers to reducing energy consumption and improving the utilization of their resources. This technique is based on distributing all services in the minimum amount of servers. This way, the overall energy consumption of the datacenter is reduced, as less servers are needed to be active. Traditionally, research has focused on strategies for consolidation of Virtual Machines (VMs), but containers are changing the landscape of Cloud services. Containers are expected to optimize the consolidation of services by reducing the amount of needed resources, thus allocating more services using less servers. However, while multiple research works have been produced in the Energy Efficiency (EE) achieved through consolidation of VMs, there is yet no experimental work on how consolidation of containers affects EE, when assuming a given Quality-of-Service (QoS) to the user. In this paper we show an experimental analysis on the effects of consolidation of containers in the QoS and EE, compared to the consolidation of VMs. We demonstrate that the consolidation of containers is indeed more optimal than the one of VMs, both in terms of QoS and EE. Consecutively, we analyze how the degradation of the service is produced both in QoS and EE, and we show how QoS is the variable which is more affected by consolidation. This work provides the necessary scientific background on consolidation of two widely used virtualization technologies, and we believe it is useful for future works on the optimization of resources in datacenters.