The answer to 'which is better variable speed or single speed AC' is that variable speed air conditioners are generally considered better than single speed models. Variable speed ACs offer several key benefits, including improved energy efficiency, better temperature and humidity control, and quieter operation.
Variable speed compressors can adjust their output in response to cooling demand, running at lower speeds most of the time to match the load. This saves energy compared to single-stage compressors that only run at full blast. Variable speed ACs also provide more precise temperature regulation and better dehumidification. And the variable speed motors are quieter than the on/off cycling of single-stage units.