The current state-of-the-art for standardized video codecs is High Efficiency Video Coding (HEVC) which was developed jointly by ISO/IEC and ITU-T. Recently, the development of two contenders for the next generation of standardized video codecs began: ISO/IEC and ITU-T advance the development of the Joint Exploration Model (JEM), a possible successor of HEVC, while the Alliance for Open Media pushes forward the video codec AV1. It is asserted by both groups that their codecs achieve superior coding efficiency over the state-of-the-art. In this paper, we discuss the distinguishing features of JEM and AV1 and evaluate their coding efficiency and computational complexity under well-defined and balanced test conditions. Our main findings are that JEM considerably outperforms HM and AV1 in terms of coding efficiency while AV1 cannot transform increased complexity into competitiveness in terms of coding efficiency with neither of the competitors except for the all-intra configuration.