Boot Camp is the first thing that come to people’s mind when they need to use Windows on the Intel Macs…but what if you want to use your Windows Programs inside your Mac OS? You could use applications like Parallels Desktop and VMware Fusion. Parallels Desktop has a longer history than Fusion, while Fusion is backed by VMware, which has a long history of making Virtual Appliances.
If you want to know which one suites you best…you probably want to read MacTech’s article on Virtualization Benchmarking.
If you wan a summary of the article above, you can take a look at MacNN’s article: http://www.macnn.com/articles/07/12/19/vm.test/
Here is MacNN’s short summary:
Parallels faster for XP, Fusion for Vista.
If someone has a Mac Pro, they are better off with Fusion in either case. Because Fusion supports multiple VM CPUs but the current version (3.0) of Paralles only supports one virtual CPU.
If you use ready made VMWare VMs (called virtual appliances), you might want to adjust their settings especially the number of CPUs and allocated memory before running them.
Another place where Fusion excels is running Linux. It provides much better integration tools (and probably better stability) than Parallels.