Use the DVI, as that will save HDMI for something else and you will get the digital signal transfer plus HD resolutions. Set the resolution to 1280 x 720 or 1920 x 1080 depending on whether it is a 720p or 1080p HDTV. If it is a 720p TV, get a DVI-D single link cable. If it is a 1080p TV, get a DVI-D dual link cable.
If your video card only has a VGA output, then get a VGA cable and use that.