I've used each and currently use Parallels. Originally I went with Parallels since it was the first. Parallels 8 for mac. Then I switched to VMWare since it used to have the better memory management. And now I use Parallels again. VMWare tends to be more polished and have fewer annoyance bugs but, currently, Parallels is faster (I think I read 20%) and has better memory management. I run Windows Server 2008 as a workstation and primarily do software development with Visual Studio in there.
![Parallels Or Vmware Fusion For Mac Parallels Or Vmware Fusion For Mac](https://i.ytimg.com/vi/DUfsDQYSs2Q/maxresdefault.jpg)
Vmware Fusion Vs Parallels Performance
![Mac Mac](https://everymac.com/images/other_images/virtualbox-screenshot.jpg)
Vmware Fusion
I did notice a big improvement when I switched to Parallels, but I also switched to Windows Server 2008 from Vista at the same time. BTW, no matter which product you go with, RAM is the most important resource. Try and get at least 4gigs in your Mac and allocate around 1.5 to 2 gigs to Windows. Also, avoid using the 3D acceleration in either product unless you know you need it. I've had tons of issues with it.