Is a projector better with a screen?
A screen provides the best quality and highest definition possible. Light reflection is the key and a wall simply cannot match that of a screen. An ultra-smooth surface is what reflects light best and since most walls have flaws, cracks or bumps, projection screens are far superior in this aspect.
Does a projection screen matter?
To get the finest possible image from your home theater set up, you must have a screen that will optimize the projector's capabilities as well as the environment it is placed in. A “Mediocre” screen will result in a “Mediocre” image, no matter how complex the other theater components are.