Ego Draconis is the original game. They then came out with an expansion pack, then bundled that with the original called the Dragon Knight Sage. The Director's Cut is the Dragon Knight Saga with a developer console. Buy that version.
as said ED version is the original game. the DC version is basically the Dragon Knight Saga version with a developer console and the DKS content so the expansion and a LOT of fixes and tweaks to the core game.
basically the ED version is pointless now.
Currently playing: Darksiders - Farcry 2 - FF13: Lightning Returns