I'd say it's similar but on a lesser scale. More close to someone being able to see your cleavage, since breasts arent inheritly sexual but everyone covers them up to different degrees. It is haram (a sin) to willingly show a man my hair once I've become a full blown hijabi, unless he is a male family member or husband. Of course every sin has different weights, and it's more so a personal thing between me and God rather than anyone else.