When comparing Parallels Desktop vs Hazel, the Slant community recommends Hazel for most people. In the question“What are the best power user tools for macOS?” Hazel is ranked 14th while Parallels Desktop is ranked 59th. The most important reason people chose Hazel is:
Hazel watches whatever folders you tell it to, automatically organizing your files according to the rules you create. Have Hazel move files around based on name, date, type, what site/email address it came from (Safari and Mail only) and much more. Automatically put your music in your Music folder, movies in Movies. Keep your downloads off the desktop and put them where they are supposed to be.
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Pros
Pro Best-in-class gaming performance
Compared to other VMs, Parallels has the best gaming performance. Still, a good framerate can only be achieved with games that have very low resource requirements. A much better option for resource intensive games is dual booting Windows (via Boot Camp).
Pro Easy to use
Parallels has an easy to learn and use UI. All important features are wizard based. It requires only a few clicks for the wizard to download and set up the latest Chrome OS, Windows or Linux build.
Pro Can run Windows apps as native OS X apps
Parallels has a "Coherence View" mode that allows running Windows applications as if they were native OS X apps. In this mode Windows is virtualized in background and Windows features like Jump Lists, Taskbar, Start Menu, etc can be embedded directly within OS X.
Pro Best integration ever
Pro Automatically cleans up and maintains folders
Hazel watches whatever folders you tell it to, automatically organizing your files according to the rules you create. Have Hazel move files around based on name, date, type, what site/email address it came from (Safari and Mail only) and much more. Automatically put your music in your Music folder, movies in Movies. Keep your downloads off the desktop and put them where they are supposed to be.
Pro Very customizable
More so than alternatives.
Pro Cleans up after uninstalling an application
When you delete an application Hazel will pop up and show you a list of attached files belonging to the deleted app to clean your uninstall more correctly.
Pro iLife Support
Hazel features new actions to import your files into iPhoto or iTunes. And with Hazel 3, you can import into Aperture projects and folders as well.
Pro Process files depending on their content
Its in-file search criteria allows it to extract dates from files (e.g., to add to the filename) and to categorize recurrent files (e.g., receipts) into subfolders (or to treat them in some specific way).
Cons
Con Very expensive
Parallels upgrades are very expensive. Even if I bough several versions of Parallels I will switch back to free VirtualBox as they even "invented" the Pro version - mainly doubled the price you have to pay each year to have the software updated.
Con Can't import OVA files
OVA files are useful because they include all of its supporting files. Unfortunately, Parallels doesn't support these useful files.
Con Requires buying a new version of the software with each new OS X release
Chances are that the same version of Parallels won't work with different OS X releases, requiring a separate purchase of Parallels for each OS X version.
Con Home edition doesn't work with Vagrant or Docker Machine
Make sure you purchase the Pro edition (the subscription) if you need command-line access to the hypervisor.
Con Can't export OVA files
One you use parallel you get trapped into a proprietary format.
Can't share disk blocks on two unrelated virtual machines (KSM for disk) too.
Con Expensive
Con Doesn't work well with subfolders
The rules don't work very well with subfolders and working with archive files (zip, rar, gz, 7z, etc) is also limited.
Con Rules creation is a time consuming process
To really enjoy the power of Hazel, you will need to progressively create more and more rules to manage each specific kind of file, but this process is slow, quite annoying when you have many similar rules, and can only be learned on the way, as you find new uses for it.