VMware Fusion and Parallels Desktop are the two apps that make it easy to run Windows software on the Mac OS X desktop, and they're so similar in features and functions that it's almost impossible to say which one you should choose. If you're a Mac user who needs to use an app that only runs under Windows, then you definitely need one of them. But you won't be able to choose on the basis of which one is more up-to-date, because recently, both came out with shiny new versions within a few days of each other.
Both let you run Windows 8.1 on the OS X desktop. Also, both programs run under OS X 10.9 Mavericks – the next version of OS X – and both let you run a copy of OS X 10.9 or other recent OS X versions in a window on whatever version of OS X you have running on your Mac. I marginally prefer VMware Fusion, for reasons I'll describe in a moment, but I have both of them installed, and I'm very impressed with Parallels Desktop's ease of use and suitability for beginners who may find VMware Fusion slightly daunting.
By the way, I wrote that VMware Fusion and Parallels are the two apps that "make it easy" to run Windows apps on the OS X desktop. You can find other apps that do far less and require far more work, notably the open source Oracle VM VirtualBox and various free and commercial versions of the WINE (WINE Is Not an Emulator) framework.
None of these come even remotely close to VMware or Parallels in terms of power, speed, or convenience. You can also run Windows on any recent Mac using Apple's own Boot Camp technology, but Boot Camp makes you shut down OS X and restart in Windows, then shut down Windows and restart in OS X. VMware and Parallels let you run (for example) Microsoft's new Windows-based Office 2013 in an OS X window while running Mac-based software in other windows – and all these apps get direct access to any OS X folder you choose.
Installing an OS
VMware Fusion, like Parallels, starts up with a wizard that lets you install a "guest" OS to run inside your "host" OS X system. Unlike Parallels, which gives you a smorgasbord of free operating systems to choose from (Android, Linux, Windows 8.1 Preview), VMware expects you to do one of these things: Install an OS from an installer CD, DVD, or disk image file; import an image of your existing Windows machine using either a network connection or a direct connection via Ethernet cable; install a second copy of OS X from the recovery partition hidden on any Mac running Lion or later; or use a Windows system that you've previously installed via Apple's Boot Camp.
If you choose an operating system that VMware supports – any recent variety of Linux, Windows, OS X and more – then VMware will install it and launch it automatically. More arcane operating systems require you to enter options by hand as they start up, just as on real hardware.
Parallels offers prebuilt options like Android from a menu, but you can find a far vaster range of prebuilt VMware machines if you're willing to search for them on VMware's site and elsewhere. (Search for “VMware appliances”).
Programmers have even written VMware drivers for arcane operating systems like NeXTSTEP and OPENSTEP, the operating systems developed by Steve Jobs that later evolved into OS X. Purely for curiosity's sake, I have both those ancient OSes running in VMware machines that I found in the depths of the Internet. But I use VMware more often to run Windows apps that don't exist on my Mac – for example, Corel WordPerfect X6 and Axialis Icon Workshop, which is, ironically enough, by far the best editing tool for OS X icons, and it exists only as a Windows program.
Compared to Parallels, VMware doesn't clutter OS X with icons and other reminders that it exists, and that's one reason I prefer it. Parallels makes it hard to clear out all the icons, menus, and shortcuts to Windows apps that it adds to the OS X interface, and its menus tend to look as if they're trying to capture your attention at the circus. I always feel as if aliens obsessed with 1960s style have taken over my desktop.
VMware's menus and shortcuts are less in-your-face, take up less room, and are easier to manage. One useful option puts a menu of Windows apps – like a miniature Start Menu – in the OS X menu bar either all the time, or when Fusion is running, or never. I hide this menu, because I only need two or three Windows apps, and I prefer to leave their icons in the OS X dock along with my most-used OS X apps.
Like Parallels, VMware lets you run Windows apps in what it calls "Unity Mode," meaning that the Windows app appears in an OS X window without the Windows desktop showing. You can also display the full Windows desktop in a window or full-screen. Parallels automatically installs Stardock's Start8 and ModernMix utilities in Windows 8, so that you can run Windows 8 full-screen apps in an OS X window and get a traditional Start menu, but you can buy the same utilities for £5 to run in VMware – which costs £20 less than Parallels, so you're still ahead by £15 with VMware.
Another plus for advanced and corporate users of VMware Fusion is this: If you have VMware virtual machines that you created using VMware Workstation on Windows or Linux, you can use those virtual machines without change on your Mac under VMware Fusion, because VMware has a long cross-platform history, while Parallels no longer offers a Windows or Linux version.
VMware has also introduced a new version for corporate users, VMware Fusion Professional. We haven't tested this, but it brings the same enterprise-style centralised control over VMware virtual machines to the Mac that long established VMware products like vSphere supply on Windows and Linux-based servers. Finally, VMware's free Windows-based VMware Player has also just been released in a new version, VMware Player 6. This lets you take a VMware machine that you created on your Mac, copy it over to a Windows machine, and run it from the free VMware Player.
Nuts and bolts
Like Parallels Desktop, VMware automatically installs all your OS X printers in Windows. VMware does this less elegantly, by needlessly adding a hash and number at the end of the printer name, so that a printer called "HP LaserJet P3015dn" in OS X is named "HP LaserJet P3015dn#2" in Windows. And VMware doesn't have Parallels' built-in feature that "prints" to a PDF – but, of course, you can always install the free BullZip PDF Printer in your Windows system.
As with Parallels, Windows and OS X share the clipboard, and you can drag and drop files from the Windows desktop to OS X, or vice versa. Again, as in Parallels, the same drag and drop feature does not work in OS X "guest" machines. When it comes to these basic functions, there's no strong reason to choose one app over the other.
Once again, as is the case with Parallels, it's easy to open folders from OS X on your virtual Windows desktop, but I prefer the way VMware treats this feature. With Parallels, by default, you'll find all your OS X icons repeated on your virtual Windows desktop, and if you don't want the same icons in two places, you'll have to hunt for the setting that removes the icons from Windows. VMware, in contrast, starts out without the extra clutter, but lets you add it from the Sharing pane in its control panel.
I haven't carried out detailed performance speed tests, but I have found that each app took almost the same time to start up Windows 8.1 – about 12 seconds on a 2012 MacBook Air with a Core i7 CPU and 8GB of RAM. You can find elaborate graphs comparing timings in Parallels and VMware, but I can't see any real-world differences worth noting.
The reason I prefer VMware Fusion over Parallels is that it's less intrusive and generally less in-your-face, even though Parallels is more beginner-friendly. Also, VMware has a long track record of reliability which Parallels can't match, even though recent versions of the latter seem to be far more trouble-free than earlier ones. Finally, the icing is that Fusion is cheaper than Parallels, too.
If you're reading this, you have all the skill you need to manage VMware Fusion, and I think you'll share my view that it makes it easy to run Windows apps in OS X in exactly the way you want to.