Over the past two weeks, both VMware and Parallels released new versions of their flagship virtualization software for the Mac. First on the scene was VMware Fusion 5 (US$49.99 - $99.99), and last week Parallels Desktop 8 for Mac ($79.99) arrived. Both offer faster performance, compatibility with Mountain Lion and Windows 8, and new features for ease of use. Now MacObserver's Jim Tanous has done a side-by-side comparison of the two virtual machine apps, complete with detailed benchmarks of their performance in a variety of conditions.
Tanous' detailed analysis shows that at least for the current incarnations of these two virtualization applications, Parallels Desktop 8 has the edge in terms of performance. He did see some anomalous results when running benchmarks on Windows 8 under Parallels Desktop 8, and chalked up the "too good to be true" performance figures to the way that Windows 8 is virtualized in Parallels 8.
There are a plethora of charts to illustrate the results, and I suggest that you look at them over at MacObserver. Tanous brings up a final point that "Consumers may not be happy with the yearly paid update cycles, but the fierce competition between Parallels and Fusion has led the market to a mature and capable state and consumers of both products will likely be satisfied with their performance."