Alexis Ahmed from Hackersploit youtube channel just made a insightful review on PentestBox, that was just recently released.
So, the premise behind PentestBox is that it comes as a very good lightweight alternative for running a virtualized version of a linux distribution.
Thus, instead of installing and running a linux distribution, like Kali Linux, in Vmware, Virtualbox, or your favorite virtualizer, PentestBox is a Windows native application that gives you a lot of tools for pentesting without putting the burden a virtualizer puts on the device.
The cool thing about it is that it has it's own browser and you can also choose to get it with Metasploit Framework installed. It also has Burpsuite and a ton of great tools you'd be using in your penetration testing assessments.
So, now the drawbacks, in my view. First, it's 2 GB, but that's the space size and not the RAMs you'd be needing for a generic virtualizer to run your distro on.
Second, I don't think it provides a sandboxed environment (like the way you can configure your VirtualBox-ed Kali Linux), so it might not be safe to test, investigate and reverse engineer malware in it. So, I guess it's a matter of personal choice.
If you're running a system with low specs and you need something that doesn't completely hog your device's resources, go for it. However, if you have plenty of RAM and a performing system, I'd still go with a virtualized version of the distro...
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Cristi Vlad Self-Experimenter and Author