Gigabyte GA-Z77X-UD3H and GA-Z77X-D3H

Whats the difference?

The UD3H has a display port, a PCIe power connetor, a fan connector more, 2 less 6Gb/s ports, an extra USB 2.0 internal connector, internal power button, clear cmos, bios switch, voltage management points, optical sound outlet, 2 esata, 6 audio ports. 

Just a few more bells and whistles. Nothing to mind blowing, but if you are an extreme overclocker go with it.