Thank you for your inquiry. Both tools are not really comparable as they do different things. Embedded Studio is an IDE and CubeMX is simply a code generator. So if you are looking for an IDE that seamlessly integrates with embOS and is well rounded and supported by SEGGER, we recommend Embedded Studio. If you are looking for a universal STM32 code generator that generates projects for all kinds of toolchains, then CubeMX can be used.