Do you need a VM?
You need to keep in mind that a virtual machine is a software emulation of your own or another machine hardware configuration that can run an operating systems. In most basic terms, it acts as a layer interfacing between the virtual OS, and your own OS which then communicates with the lower level hardware to provide support to the virtual OS. What this means for you is:
A drawback of virtual machine technology is that it supports only the hardware that both the virtual machine hypervisor and the guest operating system support. Even if the guest operating system supports the physical hardware, it sees only the virtual hardware presented by the virtual machine.
The second aspect of virtual machine hardware support is the hardware presented to the guest operating system. No matter the hardware in the host, the hardware presented to the guest environment is usually the same (with the exception of the CPU, which shows through). For example, VMware GSX Server presents an AMD PCnet32 Fast Ethernet card or an optimized VMware-proprietary network card, depending on which you choose. The network card in the host machine does not matter. VMware GSX Server performs the translation between the guest environment's network card and the host environment's network card. This is great for standardization, but it also means that host hardware that VMware does not understand will not be present in the guest environment.
Virtual machine technology imposes a performance penalty from running an additional layer above the physical hardware but beneath the guest operating system. The performance penalty varies based on the virtualization software used and the guest software being run. This is significant.
One of the key reasons to employ virtualization is to isolate applications from each other. Running everything on one machine would be great if it all worked, but many times it results in undesirable interactions or even outright conflicts. The cause often is software problems or business requirements, such as the need for isolated security. Virtual machines allow you to isolate each application (or group of applications) in its own sandbox environment. The virtual machines can run on the same physical machine (simplifying IT hardware management), yet appear as independent machines to the software you are running. For all intents and purposes—except performance, the virtual machines are independent machines. If one virtual machine goes down due to application or operating system error, the others continue running, providing services your business needs to function smoothly.
Another key benefit virtual machines provide is standardization. The hardware that is presented to the guest operating system is uniform for the most part, usually with the CPU being the only component that is "pass-through" in the sense that the guest sees what is on the host. A standardized hardware platform reduces support costs and increases the share of IT resources that you can devote to accomplishing goals that give your business a competitive advantage. The host machines can be different (as indeed they often are when hardware is acquired at different times), but the virtual machines will appear to be the same across all of them.
Ease of Testing
Virtual machines let you test scenarios easily. Most virtual machine software today provides snapshot and rollback capabilities. This means you can stop a virtual machine, create a snapshot, perform more operations in the virtual machine, and then roll back again and again until you have finished your testing. This is very handy for software development, but it is also useful for system administration. Admins can snapshot a system and install some software or make some configuration changes that they suspect may destabilize the system. If the software installs or changes work, then the admin can commit the updates. If the updates damage or destroy the system, the admin can roll them back.
Virtual machines also facilitate scenario testing by enabling virtual networks. In VMware Workstation, for example, you can set up multiple virtual machines on a virtual network with configurable parameters, such as packet loss from congestion and latency. You can thus test timing-sensitive or load-sensitive applications to see how they perform under the stress of a simulated heavy workload.
Virtual machines are easy to move between physical machines. Most of the virtual machine software on the market today stores a whole disk in the guest environment as a single file in the host environment. Snapshot and rollback capabilities are implemented by storing the change in state in a separate file in the host information. Having a single file represent an entire guest environment disk promotes the mobility of virtual machines. Transferring the virtual machine to another physical machine is as easy as moving the virtual disk file and some configuration files to the other physical machine. Deploying another copy of a virtual machine is the same as transferring a virtual machine, except that instead of moving the files, you copy them.
Which VM should I use if I am starting out?
The Data Science Box or the Data Science Toolbox are your best bets if you just getting into data science. They have the basic software that you will need, with the primary difference being the virtual environment in which each of these can run. The DSB can run on AWS while the DST can run on Virtual Box (which is the most common tool used for VMs).