Were different parts of the Pali Canon intended for different audiences?

I read somewhere that the Middle Length and Long Discourses in the Pali Canon were intended for different audiences. I think it was that the Long Discourses were intended to convert people to Buddhism and the Middle Length discourses were targeted at experienced practitioners. I could have got that the wrong way around or just generally wrong but I do remember that someone said they were intended for different groups of people. Does that ring true with anyone? Can anyone give any further details of whether these parts where for different people and if any of the other parts of the Pali Canon would also be intended for different people. I'm more thinking about the Sutta Pitaka. Clearly the Vinaya Pitaka was for monks and the Abhidhamma Pitaka would have been more advance.