I just thought the comparison between the two Jedi was interesting. It's not quite as amusing as Kennedy vs. Lincoln, but it's worth constrasting the two. The full name of Vader's apprentice is never given, so let's call him Bob Starkiller:
Luke thinks Vader killed his father, but Vader is his father. Bob is raised as if Vader was his father, but Vader actually killed his father.
Both of them find out the truth about their dad as part of their training.
Vader tries to get Luke to leave the rebellion and join the empire. Vader gets Bob to leave the Empire to join the rebellion. (It's actually even more interesting than this but I don't want to have to map out the whole plot.)
Bob had a droid from Vader, which was programmed to randomly try to kill him. Luke had a droid made by Vader, which was programmed to be a dumbass.
Vader wounded both of them in a way intended to not kill them and both end up with some replacement parts.
The throne room scenes at the end of Return of the Jedi and Force Unleashed had a lot in common.