Which is more difficult a scat or a whistle?

Which is more difficult a scat or a whistle?
In my opinion, a whistle because it takes a lot of practice to make the right technique in order to blow the air out of your mouth to make a sound. Scatting on the other hand, is a flow of any kind of words that obviously do not make sense, put them in a sort of "Jazzy" beat and then add a melody to it and your basically set.