You don't have to have a big plasma screen but, because of the letterbox format, bigger is better when choosing widescreen. With widescreen you get the same image you got at the theater; full screen cuts off the edges. It's also a matter of personal taste and whether or not the "box" of the letterbox bothers you.
Well, with fullscreen, it is what is sounds, the movie fills up the whole T.V. With widescreen the movie sort of "stretches out". Sometimes, characters and scenes might be cut out because of this. Widescreen is when there are "two black bars" in the movie, with the image in the middle. Personally, I like full screen because I'm able to see the entire movie, but really its up to what your taste is. Hope this helps!
jessica, you have it backwards.... the original shape of the movie is wide screen, just like in the theatres. when you watch the movie on a full screen (almost square) screen, they cut the image and you lost the left and right sides of the original image. in some cases, you are losing close to 50% of the image! you will sometimes see a message saying "this movie has been formatted to fit a tv screen).. this means, chop off the left and right of the image.
full screen = no black bars on a non-wide screen tv, but missing a lot of details from the left and right of the main action. wide screen = entire move (image), but black bars on a non-wide screen tv.