I
like Toshiro, I'm indifferent to Hinamori. But I just
can't stand Hitsuhina; I see them as
sibling-like friends but not as lovers.
Toshiro
needs someone who accepts him for all his strengths and faults; someone who accepts him for what he is and Hinamori just isn't that person.
In my biased opinion, if HitsuHina were to happen, it'll be a one-sided relationship with Toshiro doing all the giving and Hinamori doing all the taking. It would seem to me like Toshiro is Hinamori's 'spare tire'; a backup for Aizen.
I swear, if Aizen told Hinamori that he'll take her to Heuco Mundo during the Soul Society arc, she'll happily betray Soul Society and follow her Aizen-taichou like sheep.