As far as I'm aware, xargs still has the problem of multiple jobs being able to write to stdout at the same time, potentially causing their output streams to be

As far as I'm aware, xargs still has the problem of multiple jobs being able to write to stdout at the same time, potentially causing their output streams to be intermingled. Compare this with parallels --group. Also parallels can run some of those threads on remote machines. I don't believe xargs has an equivalent job management function.