This post is older than a year. Consider some information might not be accurate anymore.
If you want to test which USB ports and devices is capable of, you can use the VBoxManage command.
C:\Program Files\Oracle\VirtualBox>vboxmanage list usbhost
Host USB Devices:
UUID: b83e5183-8a1c-4d8d-b329-2f62515e2051
VendorId: 0x045e (045E)
ProductId: 0x00db (00DB)
Revision: 1.115 (01115)
Port: 0
USB version/speed: 2/2
Manufacturer: Microsoft
Product: Naturalr Ergonomic Keyboard 4000
Address: {36fc9e60-c465-11cf-8056-444553540000}\0016
Current State: Busy
UUID: c8543692-850b-45c1-aa44-42b9f631ca3c
VendorId: 0x046d (046D)
ProductId: 0xc063 (C063)
Revision: 87.0 (8700)
Port: 0
USB version/speed: 2/2
Manufacturer: DELL
Product: DELL USB Laser Mouse
Address: {745a17a0-74d3-11d0-b6fe-00a0c90f57da}\0008
Current State: Busy
..
