Quite a lot actually.

The biggest additions are the chapters where you control Nico. In the original BS, you can only play as George.

Then there are new comicbook style portraits whenever characters talk. There are also new graphics for some of the puzzles.

Speaking of puzzles, some of them are slightly modified because of the new graphics, and the goat puzzle is much simplified (which I consider an improvement). Still, about 90% of the puzzle are identical to the original, so don't expect huge changes or improvements in this area.

There is a journal and hints now, and finding hotspots in the environment is much easier.

You can no longer die in the game (similar to LucasArts adventures) and blood has been removed from some cutscenes.

These are a few of the changes I can think of. There are probably a few that I've missed. Overall I would say about 25-30% of the game is either new or modified content. It feels like a new experience at times.

Reforged on the other hand is more or less identical to the 1996 game, except the graphics are remastered now, while Director's Cut retains the same graphics (except for some of the new puzzles).

Thank you for your reply! So I have DC and I have no reasons to by REFORGED, as I have more content.

Originally posted by KratoS:

Thank you for your reply! So I have DC and I have no reasons to by REFORGED, as I have more content.

You're very welcome. :)
Pretty much yes, if you already own the DC, there is no urgent reason to buy Reforged just yet. Besides, I forgot to add: the DC also includes the original BS from 1996. You can install it like you would DLC, and it works great on new hardware because it runs emulated on ScummVM.