I don't actually think that it'd be right if Vader appeared behind a blast door, it would rest drama to that duel... I mean, there are lots of scenes of lightsabres in SW... some of them are fights (Maul vs Quigonn, Dooku vs anakin and obiwan, Palpatine against windu, Obi vs Grievous) but there are others that are actual duels which have a strong dramatic meaning and connotation. Both Obi Wan vs anakin/vader duels must have that drama thing, even if the ROTS duel kinda crossed the line between fight and duel...I mean they were best friends... It mustn't be just hate... It must have a sense of disappointment, nostalgia, you know, actually I'd have chosen the Anakin's betrayal theme instead of Battle as Ady did.