They both have 16 megapixel rear cameras. The front cameras are 5 megapixel for the S6 and 3.7 for the Note 4.
The screen size is a huge difference. I have a Note 4 and had a S6 Edge, the screen difference is huge.
Here in the US the N5 is close to the same price as the S6 in many places but I understand it isn't on other places.
Myself, the large screen is mist important to me, so I like the N4. The display with the N4 is very good, better with the S6.
In the Samsung forums here, there will be a forum for the S6 and the N4 and pinned threads of pictures members have taken. You can see some pictures from both.