Possible Duplicate:
Advantage of connecting laptop to monitor through HDMI to VGA
I can connect my laptop with an external monitor via VGA port or via HDMI. Which way is preferred and why?
Possible Duplicate:
Advantage of connecting laptop to monitor through HDMI to VGA
I can connect my laptop with an external monitor via VGA port or via HDMI. Which way is preferred and why?
Pros:
The HDMI cable can carry audio and video, which means one cable to bring your laptop's video and audio signals to your display (which may have integrated audio). So: cable simplification is one reason to prefer HDMI to something like DisplayPort or DVI.
Physical cable size and length (and cost) are also another reason. HDMI cables are nice and compact and can be had cheap (from places like monoprice.com) and will go for lengths of up to 100' before requiring a repeater to maintain signal integrity. In comparison a DVI or VGA cable is clunky and costly and doesn't run for long lengths without a lot of noise showing up on the video signal.
Cons:
The HDMI physical connector isn't that secure. It can be pulled out of the socket with minimal force. So if you're moving your laptop around a lot you might find the cable disconnects versus something like a D-Sub connector where you can screw it to the device to hold it in place.
I think you misunderstand the point of HDMI, which delivers video and audio over a single cable.
It's a digital signal, so there will be little difference between the HDMI and DVI output, but it will be much better than the analogue VGA output.