What's the difference between Director's Cut and Mainstream?

The Subject line says it all:
What's the difference between Director's Cut and Mainstream?

Is one longer? Are certain scenes added/cut? Are certain scenes re-shot?
You'd think this information would be readily available, due to the Director's Cut being more costly to buy, but I can't find it anywhere. Surprisingly, IMDb doesn't even list any Alternate Versions for this film.

Same thing for the sequel, by the way...