depending on the projector you have will determin if a white wall or a screen will work. I have owned 2 projectors so far, one being an infocus Lp755 and one being an infocus screenplay 7200. The Lp755 doesnt make any differenct being on wall or screen, however my Lp755 on the screen i have is significantly greatter than a wall. The screen (depending on what kind u get) will help add to the picture quality becure its not a pure white background. It helps bring out color and blacks. When it comes to this it all depends on your eye. As for a $500 screen id say u wont find much difference between the screen and the wall. What kind of screen are you looking at? what projector do you have?
Component would be your best option of the ones you listed. Above that would be DVI, but those cable can be pretty costly depending on your cable run.
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