"EDTV" and "SDTV" (as well as "HDTV") are labels created by the Consumer Electronics Association (CEA) in an effort to distinguish the different formats of digital video (quality) offered within the DTV standard [1].
Currently, within North America there are two consumer television broadcasting standards - one is digital and the other (to be phased-out by 17 February 2009,) is analog. The analog television standard is known as NTSC (named so in honor of the National Television Standards Committee that established the standard.) NTSC is limited to a 4:3 picture aspect ratio (picture width × picture height) and is roughly equivalent to the digital resolution of 640×480 pixels, (which is commonly known as “VGA” throughout the computer industry.) Also, as required by the NTSC standard, broadcast video is transmitted, as well as recorded on analog consumer VCRs, exclusively as an “interlaced” video signal, which is far less desirable than a non-interlaced (aka, progressive scan) video signal [2][3].
The other standard [4][5] being broadcast at the present time – and for the foreseeable future – is DTV (Digital Television,) which uses digital (video) technology similar to that found in the computer industry. DTV comes in three primary – or common – 'flavors' (in descending order from best quality to the digital equivalent of NTSC quality) - HDTV, EDTV and finally SDTV.
HDTV, the best broadcast digital television quality currently available, is exclusively a 16:9 (i.e., widescreen) picture aspect ratio and supports video resolutions of at least 720 progressive (p) video scanning lines or 1080 interlaced (i) video scanning lines as well as Dolby (AC3) digital surround sound.
EDTV (Enhanced Definition Television) offers improved digital television quality by offering at least 480/60p (progressive) scanning lines of video resolution in a 16:9 or 4:3 picture aspect ratio and also supports Dolby (AC3) digital surround sound. EDTV provides roughly the same video quality as that of standard DVD-Video discs with which you're likely familiar.
Finally, SDTV (Standard Definition Television) provides very basic digital television quality that may be displayed with up to 480/24p, 480/30p, or 480/60i scanning lines of video resolution in either a 16:9 or 4:3 aspect ratio and is the subjective digital equivalent of NTSC. SDTV is also able to provide roughly the same video quality as that of standard DVD-Video discs.
BTW, go ahead and spring for the digital TV it'll offer a little more in terms of flexibility and much less hassle for you in the long run.