I have used both VMware(free edition) and VirtualBox and I prefer VirutalBox over VMware.

1. To download VMware, you have to go through a registration step which requires you to have a corporate email id. Virtual box download is a breeze.
2. I could not get my VMware into full screen mode even after tinkering around for sometime. Later someone informed me that it is available only in the pro versions (I am not sure of this). Getting VirtualBox to work in full screen mode was easy as pie.
3. VirtualBox has the concept of shared folders using which you can seamlessly move files from the host box to the guest box. Setting this up was not child’s play, but once it was done it saved me tons of donkey work. In VMware, I had to use Samba to get this done and it was more difficult to set up Samba than VirtualBox’s shared folder utility.