The d3h only has one PCI-e slot, and cannot be used for multiple graphics cards (except for dual-GPU cards)
[strike]The ud3h apparently has no USB2.0 headers, which are used for front panel USB ports.[/strike] (Nevermind, shoddy Newegg descriptions. If you look at the images, it has one USB2.0 header).
The d3h has no eSATA ports for specialized external storage drives.