No the stories are going to be same length: male / female, no differences in length. As I posted already (I think?) some romance dialogues will be probably shared (a bit like what happens in Loren) changing only the gender/pronouns, but each gender will have some exclusive dialogues.
It's still early in the works so things might change, is hard to give you a reply now
But I don't plan Ace story to be a DLC or anything, will be another version of the story, same length.
I also don't know if I'll make first Lily's version or like Roommates release both versions at once, I would prefer this option so the game gets tested one time and is faster
and as Sylrissa said, is better to not make "one side" of fans waiting too much (even if of course Nicole delay wasn't planned