In what is one of the most complete and comprehensive comparisons between VMware Fusion and Parallels virtualization software for Mac, MacTech concludes that across the board Parallels outperforms Fusion. Not only in start up times, normal application execution, disk activity, and compatibility, but also in 3D graphics and gaming. If you're looking for a solid thorough comparison of these virtualization products, this is the best I've seen. You can read the entire article here.