Here's a review and comparison of Parallels and VMWare: http://www.macworld.com/news/2007/02/21/vmwarevsparallels/
I thought it was informative comparison of VMWare and Parallels. I don't use VMWare, so I found it insightful.
It was just rather dated, and failed to mention that Parallels is also in beta/RC stage as is VMWare. It also failed to mention the huge leap VMWare has in non-Windows support. The tools for Solaris, for example, make mouse movement and clipboard sharing a dream. The last released product from Parallels missed the mark and lacks essential capabilities found in te current RC3 release which pretty much means if you really need the features (advertised but missing in the GA release) you must use non-production releases. A stale article like that is acceptable in print media where there are 90-day lead times, but online articles should be current as of the publish date (which too often is missing in on-line articles, writers!!). I really recommend curious people try the VMWare Fusion product if only to see another view of virtualization in OS X. You may see something you'd like to have in Parallels, and if so this is a good time to ask about it. At the very least it is quite educational. You will appreciate some of the polish that Parallels has put into their product.
Er... the article cites RC3 of Parallels in the second paragraph, and mentions coherence and boot camp support towards the end. However, having made the statement that Parallels have a released product on sale while Fusion is only in beta they, quite rightly, go on to base their comparison on the released version of parallels. As for the unix/linux tools - yes, I'd like them too, but its worth remembering that the Big Sales Opportunity is people wanting to run Windows, so its understandable that Parallels are concentrating on that. It seems probable that VMWare's existing tools for linux/unix were host-os-agnostic and "just worked" on Fusion. Its not as if there aren't work-arounds to most of the tools (ntpd/rdate for time, nfs or samba for file exchange, Apple's X11 server for seamless mousing).
