I’ve written about this several times before, since I own both products. I keep giving VMware another chance because I really want to use it, but I keep going back to Parallels for several reasons.
The major reason I can’t use VMware is because it has problems with Visual Studio Team Server. I use VSTS for source control for my Mac projects at work, which means I need to share the Mac source folder to my Windows VM and have VSTS check in and out to it. Parallels is able to do it with no problems, but VMware always gives errors when checking out or downloading the latest version to a shared Mac folder, which occurs whether I use VMware shared folders or windows file sharing and mount it as a regular server. If this problem is ever fixed, I can consider using VMware.
Aside from that, there are a lot of things I like about both products.
Parallels Coherence mode feels a lot more polished than VMware’s Unity. If you select Coherence as the default, Parallels will automatically switch to coherence mode when Windows boots, even when it’s displaying the login window. VMware, on the other hand, can only be switched to Unity after it’s fully booted to the Windows desktop and you’re logged in. Dragging windows in Parallels looks a lot cleaner, since exposed windows show their contents immediately. With VMware, the newly exposed window will show the remnants of the window above it until you let go, when it will be redrawn.
Parallels integration between Windows & Mac OS X is also a lot nicer. You can double-click a Windows document in the Mac finder and have it open in the appropriate Windows application under Parallels. This is the closest you can get to a native feel for Windows applications. In fact I don’t have MS Office installed under OS X; I use Office 2003 in Windows XP to open Word & Excel documents when I can’t use iWork 08.
On the other hand, VMware has less impact on the system. Parallels usually slows down my MacBook Pro (2.5 GHz Core 2 Duo, 4GB RAM) noticeably, often freezing it completely for several seconds at a time.
VMware also supports Linux much better. Parallels still doesn’t have drivers for the Ubuntu 8.04 (“Hardy Heron”), the latest version. VMware’s linux tools are also better than Parallels, since it supports sharing of Mac folders to the Linux VM, which Parallels doesn’t.
While I’m unhappy about some things with Parallels, I continue to use it because I use Windows XP a lot more than I use Linux and it works much better for me with Windows.