If you plan on using video you must have a video port. Most important for training applications and home theatre. About Image Brightness Big rooms and big groups require big images. Light output is measured in units called ANSI lumens. More lumens mean more brightness, and generally speaking, more brightness translates into bigger images that look good even when the lights are on in the room.
Brighter images mean better looking presentations.
You might be pleasantly surprised at the money you'll save if you're willing to lug a little more weight around. A zoom lens allows you to control image size. Zoom lenses are a particularly valuable feature for presenters who move their projector from room to room. If you're planning on a permanent set up for your projector, consider the convenience of rear screen or ceiling mountable projectors. Be aware that rear screen and ceiling mounted projector images must be reversed or flipped in order to appear properly on the screen.