Tech review blog NightLion recently released a comparative performance breakdown of Parallels Desktop 7 for Mac versus VMware Fusion 4. This comprehensive review examined both VM softwares specifically in the areas of performance with Backtrack 5 (a Linux based testing program), with Windows Vista with Lion integration, and converting images between VMware and Parallels Desktop 7.
While NightLion did not find significant differences between VMware and Parallels Desktop 7 while testing Backtrack alone, once Backtrack was tested alongside Windows Vista, Parallels Desktop 7 pulled away, "Boot time for Vista VM measured at 3x SLOWER than Parallels. Noticeable performance lag noticed when trying to run multiple VMs".
NightLion continues by examining both software’s performance with Windows Vista with Lion integration. Parallels was again stated to have an edge. NightLion found that Parallels Desktop 7 consistently booted up faster and performed better while running heavy applications, "Running heavy applications like Visio started quickly, but performance quickly degraded as large Visio documents were opened. Performance became choppy and sluggish".
NightLion wraps up his review by declaring Parallels Desktop 7 the winner:
VMWare just doesn’t cut it when compared to Parallels’ overall performance. With Parallels, Bootup and load times are significantly faster. Overall system performance is also better when running virtual machines. In my opinion, Parallels Desktop 7 is the clear winner.