Other comparisons out there are recommending Operating Systems that are long dead or no longer relevant. This is most likely because these «Top 10 Open Source Linux Firewall Software» lists are copied from year to year by non-technical users, without doing the actual comparison.
Some Operating Systems have been superseded or simply stopped being maintained and became irrelevant. You want to avoid such systems because of security reasons – these distros use outdated and have insecure Linux/BSD kernels which can potentially expose you to security exploits.
