Perhaps you only need to run a single VM at a time. If this is the case, then VMware Workstation Player is a great solution; it's free to use and made by the industry leader. On the other hand, if free to use is a must and you need to run multiple VMs at once, then Oracle VirtualBox is very popular. For casual non-commercial use, both are free and the distinction will thus be entirely personal. Where this discussion makes a difference is for the power user building a lab of multiple VMs. If you're willing to shell out a little money, then VMware Workstation Pro is the industry standard. Workstation Pro does have an evaluation period if you'd like to take it out for a spin. At the time of writing, the price for a new license of VMware Workstation Pro 14 is $249.99. That's not exactly a value to sneeze at for many folks, so a true evaluation of the product is in order.

Here's the thing: this is a book about penetration testing, which is a professional activity. On the other hand, anyone can research ethical hacking concepts at home in their free time. If you're reading this as an aspiring or current professional, then you can't be worried about free and personal use. (If you're self-employed, that license cost is a tax write-off.) On the other hand, if you need to build a personal home lab, money can be tight (hey, decent computers are expensive). Speaking for myself, I've been on both sides: needing a hacking lab for personal study and development but also in a professional context. In the professional setting, I used VMware Workstation Pro. In my home environment, I spent a long time building a vast lab environment based entirely on Oracle VirtualBox running on a variety of physical machines. However, in the end, my personal preference is VMware Workstation Pro. I don't represent any company on this one; it's just a matter of what came out on top after some years of work in both environments. That said, there's an important point to be made here: Oracle VirtualBox is fully capable of supporting all of your needs. So what's the difference, really? The differences are as follows:

• Performance: Workstation Player and Pro are faster than VirtualBox. Workstation is better optimized for the host environment. If your host environment is powered by a beefy computer, it may be less of an issue for you.
• Snapshot reliability and cross-platform compatibility: Both products have their advantages on this one. When it comes to the free version supporting cloning and snapshots, only VirtualBox has the edge. In addition, the compatibility of a VirtualBox image is high; it will run just about anywhere. On the other hand, VirtualBox snapshots and clones can be a little glitchy.
• Overall dependability and stability: VMware Workstation, both Player and Pro, are more stable than VirtualBox. I don't even remember the last time Workstation crashed on me. I do remember it happening a few times with VirtualBox. This isn't to suggest that VirtualBox is unstable and unreliable. But when you're looking at years of use and many, many cycles of installing, removing, changing configurations, upgrades, and more, the overall stability winner is VMware Workstation.