From personal experience you will most likely see a little bit cleaner image. If your camera is CIF quality it will record in that level, you will have to upgrade your camera(s) to record and view in D1.
It also depends on what kind of DVR unit you are using. If it is a stand alone unit and has HDMI, I recommend plugging it into a nice HD monitor or HD TV for viewing/reviewing to get the best picture and quality available.
Any other questions feel free to message me.