The DVD version matches the original DVD resolution (720px wide) and its quality is almost like the one of original DVD. It fits PC, laptop or home video the best. It is for those who prefer the highest quality of both video and audio. If you have a home theatre, this version is the only possible one, because of the 6 channel surround sound and high image resolution.
DivX's stereo sound and high resolution 123movies can satisfy the requirements of most PCs, laptops and TVs. This version is smaller in size and it will take you much less time to download a movie. This version is the most popular one because it's space-saving, yet good enough in terms of quality.
The PDA version is designed for portable digital devices. (yes, you can use those, too!) Its resolution and sound are optimized for these portable devices and the size of the file is even smaller then for a DivX.