The original version is far and away the best... I'd heard that the Saturn version improved the game a bit due to its smoother framerate and better sound, but those were all lies. :/

Differences between the two:

-Jaguar version has better music during the title screen.
Saturn has really bad techno music dubbed over the title and options menus... I don't remember that in the Jag version.

-Jag version has cool "melting" transitional effects in the menus
When you select an option, the screen seems to melt and zoom in as it fades away. Nothing of the sort in the other versions.

-The music dynamically changes depending on your performance in the game, in the Saturn version it just plays.
So if you get killed in the Jag version, the techno tune becomes more subdued and usually drops down to just a drumline. Likewise, if you're doing awesome the tune really gets crazy with all the bells and whistles.

-No cool Game Over music in the Saturn version
The Jag version has this cool foreboding drumline... Removed entirely in other versions.

Anyone notice any other differences? I guess the original version is the best when it comes to Tempest 2000...