Friend, all ports on you graphics card have the same video quality. So it doesnt matter what you choose, you will get awesome picture quality in your monitor.
DVI simply carries only video signal, first to be invented
HDMI carries both video and audio signal. It can be used for only video.
Displayport carries both video, audio and can also carry data, such as music/movies
Anyways, displayport is sort of a new conection to be used in computers and conect notebooks to pass video or share data, sort of a multi-functionality port. Because its small, a single graphics card can have multiple display ports on its backplate. Thats why you see several display ports and only one DVI, because of the physical size of the conector.
Regardless, all 3 conectors have the same picture quality.