I've often worked in settings where several users have access to the same machine for computationally intensive tasks. The machines in question are standard linux machines (no docker/kubernetes or similar).

In some cases, there has been a policy to never use all the machine's cores for a given task to not hog resources. In other cases, the policy has been to run non-critical tasks with high nice values for the child processes, to allow priority to more important tasks.

Which is the better or more 'polite' way of allocating resources on a multi-user system? If neither is unilaterally better, what are the pros and cons of each?