I imagine this must have been discussed here before, but I guess I missed it, so I will go ahead and ask it. In ANH, Ben lifts his light sabre and smiles, allowing Darth Vader to kill him. I know he said to Darth, "If you strike me down, I will become more powerful than you can imagine" and I'm sure he knew he'd turn into a force ghost, but is there more to it than just that? Wouldn't it be better to guide Luke as a living being than as a force ghost? Wouldn't it be better to kill Vader, if he could (though he probably couldn't have if he wanted to at that point) ?