It depends on the sentence. There is no difference in meaning, so native speakers use them interchangeably, according to whichever one sounds most natural with the surrounding words. 'Maybe' is a bit easier to say, so that tends to be the one that's used more in speech.

Here in America I don't hear people use the word 'perhaps' in their speech nearly as much as I hear the word 'maybe'. Maybe because 'maybe' is easier to say =)