DS has a more accurate translation, cut down on the censorship, and added not only the PS1 features (things like the ending tracker were great) but some new content not available elsewhere (which is mostly pretty decent in quality, if ultimately forgettable). It is definitely the best version.
SNES is next in line, because what the PS1 gains in expanded content, it more than loses in absolutely awful load times.
Kill 1 man: You are a murderer. Kill 10 men: You are a monster.
Kill 100 men: You are a hero. Kill 10,000 men, you are a conqueror!