The more expensive the projector, the more features it will have, which may not always be desired. Only you can ultimately decide which projector is best suited for your application. The quality of any image is comprised of 4 elements. Those elements are contrast, color, brightness and how even the illumination is across the picture. Contrast Contrast is simply the difference between the brightest and the darkest parts of the image.
Contrast helps define the depth of an image, and is important when projecting video images.
High contrast is useful when displaying high quality video, but not as necessary when displaying simple computer data such as spreadsheets. The more colors your projector can support, the better. Color also helps define the depth of an image, by adding shades to the objects displayed. Typically projectors display 16 million colors or more, which is adequate for both video and computer data. The brightness level you need depends on the kind of environment in which you display your information.