I don't notice a real, definable difference between some BH contractions and 'real' contractions. The only thing that is really definable IME about BH contractions is that they aren't consistent, they don't get longer or closer together. They're not a different 'kind' of contraction except that they tend to be more mild than strong active labour contractions, but they can definitely get close! Also, I've had many types of contractions throughout my labours. Some are sharper, some are lower in the belly, some are all-over, some are in the hips or back...there is no one type of 'real' contraction for me. It depends on the baby, the progress of the labour, the position of the baby, etc.