MacTech performed an exhaustive set of benchmarks comparing Parallels, VMWare Fusion and Boot Camp to run Windows on a Mac.
To tackle this problem, MacTech undertook a huge benchmarking project starting in September. The goal was to see how Boot Camp, VMware Fusion, and Parallels performed on different levels of Mac hardware, covering both Windows XP and Vista, and comparing that to a baseline PC running Windows.
Doing such an exhaustive comparison resulted in 19 configurations tested with over 2500 tests to be completed. They tested 3 different broad scenarios: one step tests, multi-step tasks between Mac OS X and Windows, and quantitiative benchmarks on a MacBook, MacBook Pro, Mac Pro and a Fujitsu Lifebook A6025.
One Step Tests: In XP, Parallels is 17% faster than VMWare Fusion on XP and 1% faster than Boot Camp. In Vista, VMware Fusion ran 46% slower than Boot Camp, and Parallels ran 44% slower than VMware Fusion.
Multi Step (Cross platform) Tasks: Parallels was 6x faster than VMWare on XP, and 5.2x faster on Vista.
A number of application specific benchmarks were also undertaken using Microsoft Word, Excel, Outlook, Internet Explorer and more. These results are detailed in their article along with relevant graphs.
Their final conclusion, however, sums up the results as follows:
... both VMware Fusion and Parallels performed well, and were a good user experience. That said, Parallels was somewhat faster in general than VMware Fusion for XP. If you want the best virtualization performance for Vista, then VMware Fusion is your choice.
Of course, if you are not interested in coexistance with Mac OS X, naturally, Boot Camp is your best option.
Note: both Parallels and VMware Fusion have been updated since these benchmarks were performed. Since VMware has multi-core support, the author speculates that specific multi-core tasks may perform better on VMware than Parallels, but these scenarios were not tested. In the tests they did perform, however, they saw no speed advantage from VMware's multicore support. That being said these earlier Crave benchmarks suggest that the VMware multicore support is a substantial advantage when performing their multimedia multitasking test.