More zoom = brighter picture and less contrast. Less zoom = less bright and more contrast. It depends on what you need. The HD1000U has plenty of light output for a dark room at that size, so minimum zoom or somewhere in between would probably be best for contrast.
The difference between minmum and maximum contrast may or may not be a noticeable difference to you. The only way for you to really tell is to try the same screen size with both maximum zoom and minmum zoom displaying the same images.
The difference between minmum and maximum contrast may or may not be a noticeable difference to you. The only way for you to really tell is to try the same screen size with both maximum zoom and minmum zoom displaying the same images.