Still, state machines are faster because each task is divided into small fragments by the programmer. Debugging a timeslicing system can be extremely difficult. State machines are significantly easier to debug. State machines operates independently of interrupts, and the individual states can be transmitted to the outside world and displayed on a monitor. This have shown to be very efficient during debugging.
State machines scores highest on the reliability issues also.
Because of the interrupt mechanisms, both application and RTOS bugs are often not easily reproduced. Using the reset button is not satisfactory on a real-time system. State machines operates without a RTOS kernel and without the interrupt mechanism. Easier code writing seems to be the only advantage of a timeslicing system over state machines. The idea of Deterministic Multitasking is to make state machines look more like system processes.