Ok this is what I found.
On the LaserDisc, there are a few unused scenes, like the drawbridge scene that every home port has included since then, that were only used in the European EEPROM board. The US ROM board never used these rooms, so America only got about 3/4ths of the bargain that Europe got. The cabinets differ as well. In the US cabinet, the score/lives P1/lives P2 is constantly displayed on a LCD numerical display in the cabinet. The European cabinet from Atari moved this to a separate screen after each level. Mirrored levels also occur more often in the US board on the account of the unused scenes needing to be replaced.
Revisional Differences
In later releases of the game's EEPROM board, the US version would eventually get the drawbridge scene by revision E. Revisions A-D all removed the drawbridge scene from the beginning and started the game with Dirk entering the castle. Revision F had the scenes all in one set order to avoid LaserDisc players being ruined by the constant skipping needed for the game's random scene orders seen in earlier revisions. However, the unused rooms that eventually would become used by the PC-DVD port of Dragon's Lair in 1997 are still on the laserdisc, but placed at the end of the laserdisc to avoid the game skipping said unused scene before going to the next used one, making the game seem both fluent and constant.
