Good morning from sunny Southeast Queensland where the weather is to die for but I'd rather live to enjoy it.
atanere, as is often the case, it seems, had/has similar thoughts to mine and got in before me while I was hanging out the washing. Mundane, for a Wizard, I know.
Likewise the quote he has placed, I would have duplicated, with the question -
What is it you wish to achieve?
I have a little experience with Kali, which I have on two computers, but have yet to make myself properly acquainted. Likewise with Parrot, and I will be installing its latest offering, v3.8 either today or tomorrow.
Both of the above are Debian-based, but it is the RPM-based Distros whom many consider to be industry leaders in pen testing.
Red Hat, formed in 1993, provided for desktop users for a number of years, and virtually pioneered Linux server technology. With that success, it went to RHEL (Red Hat Enterprise Linux) in the mid-noughties, and as part of that, included proprietary elements in its software. However, its open source option, Fedora, remains free and open source.
Red Hat's expertise was pivotal during the "shell shock" aka Bash Bug dramas of September 2014, which occurred around the time I was migrating to a totally Linux environment.
A similar story, vis-a-vis commercial Linux applies to another of the old-stagers from the 90s and also RPM-based, and that is German-based SUSE. It trades nowadays as SLES (SUSE Linux Enterprise Server), and too, it has its form for us users in OpenSUSE.
I mention the above, not to air my knowledge, but because this may be relevant to you and to others of The Viewers.
If you are familiar with MCSE (Microsoft Certified Software Engineer), then each of the above firms engage in Linux certification.
There are courses available through them, I am not aware of the costs, but I would be surprised if pen testing did not feature highly.
You could Google up eg "Linux pen(etration) testing", and be aware that search engine DuckDuckGo, which is an option in the Mozilla Firefox browser on many Distros -- whilst its output page is annoyingly long for my liking, it is possibly more focussed towards generating Linux -oriented answers.
Another term you could search under that is often used these days is "ethical hacking", and refers to the "White Hat" approach to security.
Cheers
Wizard