Damn it Fern, now you have me questioning my decisions and harping on the different depictions.
It would seem at first glance that overall, doing Here Lies The Abyss first brings about the best results.

Here wee see Celene sitting on her throne, high and Golden, the lack of shadowed black also bods well. The main difference in this depiction is the assassin, clad in white and standing right beside Celine Rather than further down. The white in my opinion indicates that this person is trusted and the fact that s/he is beside Celene would indicate that she is close to them. The white could also indicate that the assassin does not need to hide any longer and is exposed, but not caught. The dagger however is black, meaning that the assassin is dangerous and because of his/her position, can strike with deadly intent. Then there's the people in the ball. In this picture they are also surrounded by white. I believe this indicates that they leave content with the outcome from the events that happened at the Winter Palace. So what if the nightmare demon didn't just affect the grey wardens. What if it also affected the Orlesian people. It could have created civil unrest that led to the civil war or worsened the ensuing chaos and fear. It could also have affected Celene and her advisors personally to weaken the political power & stability in the region, to make them ripe for the picking. That would make sense given Corypheus' plans.
As for The Here Lies the Abyss fresco, I wonder what the runes imply. I'd contend they are a positive thing but I have nothing to back that up with really. Could they represent a binding of sorts? Why would completing Here lies the Abyss before Helping Celene have an impact of that kind? Maybe the clue is in the name? Wicked Eyes and Wicked Hearts, also pertaining to the nightmare demon?

Then there is my Fresco. I always did Wicked Eyes and Wicked Hearts first, so I never saw a different depiction and for that I thank you Fern, wouldn't had even known it existed if it wasn't for you 
Here lies the more ominous depiction. The people are nowhere to be seen, overshadowed, as it were. The Assassin here is still lurking in the shadows much further away from Celene. Although he seems more menacing, his/her dagger is white. This makes me feel like s/he isn't a threat yet. They are not positioned right yet in order to strike. What interests me most however is that Celene is not on her throne but rather she seems to be standing in front of an eluvian, alone. The eluvian is also depicted with black, as if foreboding with ominous and mysterious events yet to come.
Anyways,if any of you guys saw differences having played both orders let me know. I'm interested to hear your interpretations as well.