David Baron wrote:
Qemu will run most anything and without the need of guest-modules which may or may not be available for the target guest or may or may not install their successfully. Qemu presents standard "hardware".
Qemu is also dog slow since it is virtualizing everything instead of paravirtualizing like the other options are.
Xen will run linux--no windows.
False. Xen on an AMD-V or VT-x capable CPU will run Windows. In fact VirtualBox and VirtualPC both are now capable of using those extensions to speed up their performance.
For my (non-)money I'd go for VirtualBox for the ease-of-use vs. licensing/performance. I'd love to get Xen working for my router box but I doubt that'll happen any time soon. For just user-grade virtualization VB is dead-sexy-simple to run and use. Also, for those who are not so worried about FOSS but want to remain legal-and-free-as-in-bear their non-FOSS license is hard to beat. From http://www.virtualbox.org/wiki/Licensing_FAQ here is item 6 (*** emphasis mine):
"What exactly do you mean by personal use and academic use in the Personal Use and Evaluation License?
***Personal use is when you install the product on one or more PCs yourself and you make use of it (or even your friend, sister and grandmother). It doesn't matter whether you just use it for fun or run your multi-million euro business with it. Also, if you install it on your work PC at some large company, this is still personal use.*** However, if you are an administrator and want to deploy it to the 500 desktops in your company, this would not qualify as personal use. Well, you could ask each of your 500 employees to install VirtualBox but don't you think we deserve some money in this case? We'd even assist you with any issue you might have."
Normally "personal use" is a euphemism for "non-commercial use". The fact they spell out the difference and explicitly state that you can use it for personal commercial use, even inside a company, just makes the easy-to-use version quite sweet.