My argument for Hayden:
1. At no point in any of the movies does Anakin look like Sebastian Shaw.
2. I think Anakin would want to look like how he did before he went to the dark side/was disfigured.
3. Brings the saga full circle by fitting with the PT.
The argument for Shaw (and why it's a bad one):
1. "Seb Shaw because that's how the original was," this is a fan edit, by nature things will be changed. How things were originally should have no bearing on the decision.
2. "I hate Hayden and the prequels," this is probably the main reason why people don't like the addition of Hayden, but I think it's stupid. To hate a 5 second shot because it reminds you of something you hate is just dumb to me. The shot of ghost Hayden is not the prequels, it's just a shot of ghost Hayden.
3. "The audience/Luke would be confused," this is incorrect. The confusion factor would be the same for both Hayden and Shaw. Like I said before, in none of the SW movies does Anakin look like Shaw. In AOTC and ROTS, Anakin looks like Hayden. So for those who have seen the prequels, there would be no confusion. For those that haven't, seeing Hayden would be just as confusing as seeing Shaw, which is to say, not confusing at all. It is VERY easy to infer who ghost Anakin is supposed to be, especially the ghost were to be placed at the funeral pyre instead.
So as you see, Hayden is the clear choice. Making the ghost Hayden, however, would upset a great many people. This is one of the many reasons why I think Anakin's ghost should not be in the film at all. Other reasons are:
1. I know Qui-Gon was able to discover the power beyond the grave, but for Kenobi and Yoda they needed to learn. It almost makes sense that they could have taught Anakin after he was dead, but then why didn't they teach the other dead Jedi? I feel I need to go with the PT explanation for Force ghosts. In the OT, Vader being a ghost is practically a continuity error. Many people thought that when Jedi die, they just become a ghost. This can't be correct though, because Obi-Wan says that he will become more powerful than Vader can possibly imagine. So Vader being a ghost is a little bit of a head scratcher. It is kind of an unexplained moment. Aalenfae said that when he's editing ROTS, he tries to get rid of anything that isn't explained in the movie. So I would do the same here.
2. The biggest reason why I'm against it is that if Anakin doesn't turn into a ghost, it makes his redemption much more bittersweet. When ROTJ ends, Vader's dead and you're actually sad. Then, oh wait a minute, ROTJ is a happy movie, now Vader's a ghost too! Vader was really evil at one time. I feel there needs to be a consequence for that. Having him be dead, and unable to find life after life, would be a much more poignant end to the saga. I think that the Star Wars series is too serious to simply cast the over-happy ending off as part of the fantasy. My biggest beef with ROTJ (and I'm not alone here) is that the movie is way too happy. Vader is EVIL for almost 4 movies. Consequence is necessary. That's why they killed him. Also, it gives the final conversation between Luke and Vader MUCH MORE meaning. I mean honestly, think of that conversation and then think about how Luke and Vader can talk again whenever they want.
In the end though, I think the best compromise would be to put Hayden Anakin at the funeral pyre, only if he disappears shortly thereafter, signifying that he was redeemed, but is not allowed to remain among the living.