Here's the second article comparing these two virtualization products. It's pretty much what I expected, except for a performance difference. I honestly was expecting the open source one to perform better, especially considering it didn't have the GUI front end like VMWare fusion does.
I agree totally with his recommendation, that if Virtual Box suits your needs, use it, if you want a nice front end and a little easier tool to use on a desktop Fusion is worth it's price.