Well, I would say Kuroha is the better deal. Sly she may be, at least she knows exactly what she want and spare no effort in getting it. Shirokusa on the other hand, saying you had a boyfriend, in the presence of Haru no less, whether it's true or not is just .... nope, that's a big nope for me. And I usually all it for long black haired girl.
Haru though, if he winds up getting scammed on of this days, I won't be surprised.