The high breakdown voltage, good thermal properties, and (in case of GaN) a higher field effect mobility compared to Si make the expected performance of GaN and SiC based power devices to be potentially vastly superior to that of the today leading power device technology - Si Insulated Gate Bipolar Power Transistors (Si IGBTs). After many year of development, commercial SiC power diodes and MOSFETs now outperform recent Si IGBTs and are poised to compete in the renewable energy and electrical vehicle markets. The recent generation of the hybrid SiC-Si IGBT modules combine the best features of both competing technologies.. These device hybrid modules handle powers up to 350 kW range at voltages well over 1 kV and have several times higher switching speed than the recent generations of Si IGBTs. SiC power technology is more mature than GaN power technology. However, the GaN enhancement mode High Electron Mobility Transistor (E-HEMT) on Si technology reached power ratings over 10 kW operating at 200 kHz with lower switching losses than Si MOSFETs and SiC MOSFETs. GaN devices already take about 20% of the RF power market with expectations of reaching 40% by 2025. Still, the existing device designs are not fully taking advantages of the superior materials properties of GaN. The lateral-vertical designs for a higher breakdown voltage; quantum well channel designs limiting high electron injection into the buffer layers; a low conducting passivation making the electric field distribution in the gate-to-drain spacing more uniform and therefore increasing the breakdown voltage, improving reliability, and increasing lifetime; perforated channel designs for decreasing the effect of the parasitic resistances and increasing the switching speeds are the innovative design features poised to improve the competitive edge of SiC and GaN technologies. For ultimate performance, the Si substrate in the GaN on Si technology should be replaced by SiC or even diamond, even though in a short run it would be hard for such technologies to be cost competitive. In a more distant feature, even diamond by itself might emerge as superior high power material. In a more near future, AlInN/AlN/GaN on Si technology could become a leading technology for high power applications.