Is it better to make a program without RTOS, all in the HAL / Common, or is it better to make Threads, one for the management of inputs and outputs and another for communications?

Hello everyone

I'm going to start developing the first program with a Renesas Synergy S124 micro.
The program should control a few inputs and outputs and communication 485.
My question is whether it is better to make a program without RTOS, all in the HAL / Common, or it is better to make Threads, one for the management of inputs and outputs and another for communications.

Thank you very much in advance.