Quote from xvcd.com :
"XVCD is an alternate VCD format. The X stands for eXtended VCD, but unlike regular VCD, or SVCD, it is not an officially recognized format. XVCD uses a higher bit rate (3.5Mbit/second) as opposed to VCD (1150Kbit/second), which results in a better image quality, but this is at the expense of more time, which makes it impossible for the format to contain more than 25 minutes of material. This makes it great to archive a half hour TV show, but you would need at least four XVCDs to store the average feature film.
One of the main advantages of XVCD is its ability to accommodate higer resolution program material, such as PAL or NTSC as opposed to regular VCDs which can only play CIF format files.
Furthermore, since XVCD isn't officially recognized, manufacturers of standalone players aren't concerned with making their units XVCD compatible. VCDs are not commonly found in the Western world, but the they have virtually replaced VHS in China and other Eastern countries. "