When comparing NoSleep vs Virtual Box, the Slant community recommends Virtual Box for most people. In the question“What are the best Mac OSX apps for someone that's new to Apple?” Virtual Box is ranked 15th while NoSleep is ranked 26th. The most important reason people chose Virtual Box is:
It works for Windows, macOS, Linux, BSD, and many others.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Lets you close the lid of a laptop
The laptop will not sleep even if you close the lid, but the display will sleep. If your display cannot sleep, simply lower the brightness until it goes dark & turns off.
Pro Compatible with Many Operating Systems
It works for Windows, macOS, Linux, BSD, and many others.
Pro Beginner friendly
A virtual machine can be set up in minutes if a ISO file to load is already available.
Pro Works well and fast for Windows host and Linux guest
Pro Free and open source
Pro Many free images available
Though most are linux flavors at https://virtualboxes.org/
Oracle's virtualbox site has others.
Pro Can do snapshots
Pro A lot of customization
VirtualBox has multiple virtualization options. Each one may be tailored to the guest operating system’s needs. This makes it especially good on virtualizing older systems, such as DOS, obscure distros, etc.
Cons
Con Discontinued development
Latest release was November 15th, 2014.
Con Lacks video performance
Virtualbox has a hard cap of 256MB of video memory. This could make newer operating systems run slower.
Con Minimal CPU customization
You can only enable/disable certain features. You cannot cap the speed of the CPU, which is required to run systems such as Windows 95.