Hyper-V or VirtualBox?

I am running Server 2008 R2 Enterprise on a new physical server. I want to take two old server 2003 Standard boxes, an application server and a small database server, and turn them in to virtual machines on the new server. I have used Disk2VHD to create virtual drives of each server.

At this point I can choose either software, Hyper-V or VirtualBox, but both seem to have strengths and weaknesses. Hyper-V seems a little bland but has good looking VM backup and redundancy features. VirtualBox looks like it will be easier to attach USB devices, the app server has several devices attached already.

If any of you have experience with both, I would greatly appreciate you input. Thank you.