Arduino vs. Raspberry Pi in Control Systems
I believe the Arudino has better hardware support, a real-time clock and due to itself simplicity creates a better platform to interact with external hardware in real-time.
The Raspberry Pi, however has a much more powerful set of processors, more memory and a general purpose operating system making it a more suitable choice for general purpose, sophisticated software, such as communicaitons and control software.
Assume a Distributed System
Combining the Raspberry Pi and Arduino, or similar SoC / MCU’s, like for example the NVIDIA Nano with an esp32 wifi module can make for some very flexible and powerful designs.
Of course that does come with a bit of a cost, in communication and messaging, which means such a sophisticated system needs to be designed with care.