Investigating the Islamic traditions considering Prophet Mohammad's states when the revelation occurred

In Sunni and Shia traditions, there has been quoted different states for Prophet Mohammad (PBUH) when the revelation occurred, and it occurs to mind whether there is a relation of the kind of revelation and the situation that occurs for the Prophet Mohammad (PBUH)?
According to the evidence, it is concluded that when the revelation was sent directly to the Prophet (PBUH), he felt hardship and difficulty heavily and this kind of revelation has been the most severe form of revelation but when the revelation was sent by an angle, he did not feel any hardship or difficulty. Also, in cases that the angle of revelation appeared to him in a human form, there was not observed any change in him, and this has been the easiest way of descent of revelation.