FreeNAS is well suited for most storage serving scenarios, whether it be for an office file server, backup destinations, data replication across the internet, or as backend storage for virtual machines. It can serve various types of clients via a plethora of standard protocols and can easily integrate with existing infrastructure using LDAP authentication and so on. It's pretty simple to use (it helps to have at least a basic understanding of the underlying technologies) and almost maintenance-free. One scenario that springs to mind that it may not be appropriate for (yet) is as S3 storage. However, S3 functionality was added in a recent release and may have improved greatly since then. I'm sure it will eventually work very well for this.
Kali is quite honestly appropriate for use on a Test Lab, a Virtual Machine, it will even run on a Raspberry Pi. It is the most popular tool used in most all training courses. It can be uses in home labs, work labs and production environments to perform real life scans for vulnerabilities among other things. It is the most popular tool for Cybersecurity tool.
FreeNAS effectively uses all resources really well and it is highly recommended for in premises NAS. It has unlimited ROI as it is really free and open-source. The only payment we need to pay is when we need any support from those guys. FreeNAS helps us to effectively do our work with the legacy systems as it manages all the components really well. FreeNAS although rebranded to TrueNAS will still be there until our legacy systems run.
The hard feature to be beat Kali with is the amount of preinstalled tools. I.e. Ubuntu is great but you would have to install each and every tool separately
Till now Kali Linux have not made a single penny negative impact on our companies business , its so powerful and useful at the same time for our company.