If I were to compare the Long Goodnight to the Big Sleep I would say that Marlow's character was more confident. Detective Marlowe seemed  to have more authority.  I think that the Detective in the Long Goodnight was passive in the way that he initially dealt with the police, the ganster and even his friend.  But Detective Marlowe has a respect for the way that he deals with his cases so he's diciplined in how he handles the information that he comes across.