The 722k is based on an incrementally improved chip (slightly faster), is a little less prone to overheating, and if you have the OTA module, it has two antenna tuners instead of one. If you don't have the OTA module, there's no antenna tuner at all. The 722k is hands-down a better box, if you have the choice, especially if you use your terrestrial antenna. If you don't use a terrestrial antenna, the 722k is still superior, but may not be worth the cost difference.