Certainly you will need to know your stuff with helicopter POF, based on current experience. The same with other subjects as they are trying to get rid of the database queens.
Having said that, you will not pass without them, not for learning the questions but for getting used to the idiocy. I ask you, of what use is the knowledge of the drop size in nasal sprays?
Of the two I keep a watch on, aviation exam has more different questions and about 10% less duplicate questions than ATPLQuestions. Both of them do not have everything by any means, and I guess that goes for the others, unless they manage to steal the database, as used to happen. I know that because I used to have access as a question writer and I have only seen a few even of the ones wot I wrote. Others tell me the same.