Both C and C++ are commonly used for programming microcontrollers, and either one could potentially be used for home automation projects on Android. In general, C and C++ are both suitable choices for low-level programming tasks, such as those involved in working with microcontrollers, and the choice between the two languages often comes down to personal preference.
That being said, C++ may offer some advantages over C for certain types of projects, particularly those that require object-oriented programming or that involve larger codebases. C++ also has a larger standard library and a wider range of features than C, which can make it easier to write certain types of programs.
Ultimately, the best programming language for a home automation project using a microcontroller on Android will depend on your specific goals and requirements. You may want to consider factors such as the complexity of the project, the resources available to you (e.g. time, expertise, tools), and your own familiarity with the different languages.