Regardless of which technology you choose, options for scaling the various aspect ratios can be important; entry level models will not have many. Aspect ratio is a ratio of the screen's width to height. A quick primer for the uninitiated;
1.33 or 4:3 = standard TV and computer monitors
1.78 or 16:9 = HD format monitors
1.85 = 35 mm US and UK widescreen standard for theatrical film.
2.35 = 35 mm anamorphic from 1970 onwards. (won't go into anamorphic here :-)
Comparison of three common aspect ratios constrained by the screen diagonal size (the black circle). The rectangular box (blue, 2.39:1) and middle box (green, 16:9) are common formats for cinematography. The box with sides of similar length (red, 4:3) is the format used in standard television. Courtesy of wikipedia and its entry on aspect ratios.
These are the most common aspect ratios but the history of cinema is peppered with variations on the format depending on when the movie was shot and which lenses and film processing they used. You will notice this more or less when renting DVDs from different eras. Computer sources have standardized resolutions at 1.33 but sport variations on the main themes. This is where the scaling or zoom function comes in handy; it'll give you the option to watch the DVD "letterboxed" at full width or crop the sides filling the screen top to bottom for movies shot in a higher ratio. You could "stretch" the standard 1.33 TV signal to fill the HD monitor side to side, with the obvious stretching of the content, watch it at 1.33 thus not using the sides of the monitor or cropping the top and bottom of the image thus filling the monitor side to side. Confused yet? Ask for the remote before you buy :-)
How much image you want onscreen becomes a matter of personal preference.
