I can see that school of thought I suppose. If you said that Anakin had ceased to exist as soon as he turned to Vader then it makes sense to have the young ghost. You could almost make a case for it not seeming incongruous next to Alec Guinness rather than Ewan McGregor.
However, that whole argument comes up against the premise that you see the back of Anakin's head in V, and then a full face shot in VI before he dies. Anakin is clearly a man in middle age and so has aged in all the time in Vader's armor. Therefore, Anakin does still exist in those brief minutes between turning on the Emperor and his death. So the ghost should be of the original actor. In this case, making it Christiansen is suddenly incongruous in the line-up next to Guinness. Now, by elbowing Christiansen into the line-up, the other ghost almost has to be McGregor for it to make any sense. The ghosts would then both at least relate to how the characters looked at the end of Sith.
Basically, what I am saying is the ghosts should be of the characters at the time of the their death, and the only way that works is with the original undoctored shot from 1983 version of Jedi.
