Visually you'll notice nothing. It has other advantages that make it better though just like HDMI has advantages over DVI as well cus they can do more and support more than just video.
Here's from wiki:
Advantages over DVI
Slimmer cables and a much smaller connector that doesn't require thumbscrews; connector pins don't run the risk of bending if improperly handled (the connector being much smaller than the DVI connector exposes it to other problems however; it's much more sensitive to breakage due to cable "tugging", the same problem that has been seen with the SATA and USB connectors).
Based on micro-packet protocol.
Allows easy expansion of the standard
Multiple video streams over single physical connection (introduced in version 1.2)
Long-distance transmission over fiber optic media
Designed to support internal chip-to-chip communication
Can drive display panels directly, eliminating scaling and control circuits and allowing for cheaper and slimmer displays
Aimed to replace internal LVDS links in notebook panels with a unified link interface
Compatible with low-voltage signalling used with 45 nm CMOS fabrication
Supports both RGB and YCbCr encoding formats
Auxiliary channel can be used for transmitting bi-directional USB, touch-panel data, etc.
Fewer lanes with embedded self-clock, reduced RFI.