I've gone for She's Lost Control over the others because Joy Division made it brilliant not once but twice. Two totally contrasting takes on the song, as opposed to the evolving versions of the others, particularly LWTUA.
For me the original lp version is simply THE best song ever - by anyone. IMHO, that this song represents the band at their peak. Bass and drums forcefully underpinning Ian's vocal and one of the best riffs Bernard ever played.
Oh yeah and Ian's accompanying dance.
The re-recorded 12" versions (with or without the fade out ending), show that the band were not afraid to deconstruct a song always acknowledged as one of their classics and give it a whole new sound.
I suppose on any other day I (or any other fan) could easily elicit their own feelings of any of the other five, or indeed any of the other 40 or 50 JD songs, and thats why Joy Division are the best band ever.
It's just that She's Lost Control is my personal favourite.