Indeed, it was not specified at the beginning of the discussion what are the constraints of the project, such as: development time, cost, speed performance, size, etc ... which in fact would have a substantial impact on the choice of the approach to be adopted, but there may happen situations where a single core, whether in RTOS vs Linux cannot meet alone the whole solution, needing either the aid of additional core or peripherals.
There are many applications for industrial environments running on Linux-based platforms, and the compatibility with this system is itself an attractive due to a certain backward compatibility, particularly if used as much as possible shell scripts. From my own experience, I can affirm that I got surprised to see the speed that can be achieved even in a core Cortex-A8, doing processings at considerable speeds, therefore, depending on the project requirements, all options should be considered prior to analyse the pros and cons.