Both animes contain lots of H-material. Although there are no scenes of sex in Nisemonogatari, I can't say for sure which one of them is more obscene.
But ecchi genre is not the only thing they have in common. Also, there are two sisters in both these titles, one of wich is sporty and another one is hysterical. Moreover, there are bra size 45 class reps, who have a crush on the main character.
If you're not the type of a person, who only admires godlike SHAFT style while watching Nise and doesn't pay attention to the content of the show, you'll like Aki-Sora.
If you liked Aki-Sora, you'd better watch Nise ASAP, because it's the same thing plus some humour, plot and godlike SHAFT style.