I've not heard anything negative about either side, and I've used both.  Personally, I think it boils down to a matter of preference.

I've worked with LOTS of virtualization hypervisors, and ultimately I would agree with hayabusa.  It's a matter of preference.

VMware has been in the industry the longest so VMware Workstation or VMware Server have typically been the preferred choice.  VirtualBox is open source, so if you like playing around with code you can do that.  Even Microsoft VirtualPC is easy to use if you're in a Windows environment.

It used to be that VMware was the only vendor with USB passthrough, but now the other vendors have that technology too (though I have honestly had problems with USB in VirtualBox, but those problems were from a few versions ago and may have been addressed).  I'd say it comes down to the reliability and capabilities in the VM tools that get installed on the VMs.  In my opinion, VMware still has the upper hand in this area.  But, again, it's a matter of preference.

As others have already mentioned, it's a matter of personal preference. I've tried both vmware workstation and virtualbox but prefer to use workstation as I've been using it for a long time and feel comfortable with it. Also, vmware workstation in my opinion is the most complete virtualization platform out there. With virtualbox I've often heard other people having problem in networking. If you haven't faced any issues till now then just use virtualbox. The latest version of virtualbox is actually very good.
You might also want to check out the below link. I'm a regular reader of this website and have learned a great deal from his articles
http://www.dedoimedo.com/computer_software.html#virtualization

Thanks!

But what about wireless card support? I haven't try any of them with a wireless card or a wireless USB dongle, but reading http://www.ethicalhacker.net/component/option,com_smf/Itemid,54/topic,5519.msg28935/topicseen,1/#new makes me wonder if one virtual machine is better than another one, as far as driver support is concern...

And yes, I agree the VMware products look better on a resume.

I am with everyone on this one, it's a matter of preference.   I would only add that I prefer a bare-metal hypervisor.   VmWare ESXi is free and will allow you to run more VMs on a single machine, assuming your hardware is supported.