I not up to this part yet after playing this game for 120 hours. Someone please type spoiler next to the title. To me its very grey. He help me but he was a very bad boy. I know its a long time ago. This is like 'The Pitt' in Fallout3. Take the cure or not. Dose it change or not. It did not change that much in The Pitt and I pick both side with different characters.
The pit has an implied http://tvtropes.org/pmwiki/pmwiki.php/Main/MortonsFork in that there is always going to be slaves no matter who you side with. (You can also choose to peacefully resolve paths with speech checks too or even switch side in the middle of the last quest).
In Skyrim's quest there is a choice between ignoring it or killing him so technically it is significantly different than attempting to free slaves* (without consequence). In Fallout 3 neither side is particularly repentant about the state of their DLC area as they still have the slaves around and the slave dialog never changes after so they basically remain slaves even though you fought for their freedom. In this case your judging a single character for execution which is a lot more cut and dry as in one case he lives and the other he is dead. (Was bad but then is good now so killing him is like what kelticpete reason is: deny the possibility of hope, redemption, etc...)
Without any dialog options with the Blades the quest doesn't actually have any alternative paths other than taking the third option of ignoring it till it vanishes. In the Pitt you have an illusion of choice with about one outcome of weapons and items from the person of your choice. (And if looked in retrospect, if it doesn't change the working conditions then why kill an entire town just to replace the leadership with the same thing)(At least in this case Paarthurnax will literally try to change things for the better)
What is better then gray/gray morality or simulated real morality (http://tvtropes.org/pmwiki/pmwiki.php/Main/MoralityKitchenSink?from=Main.FullSpectrumMorality). And as TES is a fairly diverse universe there are a lot of black/gray/white, blue/orange, and every shade inbetween due to the variety. Which is good but at the same times the Blades are just illogical in Skyrim (Use call dragon in front of Delphine, Look its the previous right hand dragon).