There's a very good tool available that will let you compare the different VM managers available at: http://virtualization.softwareinsider.com/
It allows you to set specific parameters that you might be interested in to find the best fit for your needs.
VMWare and VirtualBox. Although I use VirtualBox almost exclusively because of how easy it is to set up. I've never had a problem running it with several different Client OS. Several different versions of Windows, Several other Linux based releases, and even a couple Hackintosh setups. As for reliability, I have never had any guest machines crash. I haven't really compared the resource usage between the two, but I'd have to say that on VirtualBox it is pretty light.
If you have any questions, please let me know. Otherwise, please take a moment to rate my service today. And if you ever have any problems in the future, please feel free to request me by going to: http://www.justanswer.com/computer/expert-bryanmohr/