For the camera, only difference is the lens. Otherwise: Same OIS/Same lens. There may potentially be IP changes as well but not sure. In any case it appears the lens+IP changes are helping it out a lot.
If you think you may use the s-pen a lot, there really isn't anything comparable right now to the note 4/s-pen functionality. I had a note 3 and loved it, I did have to rock it without a case for 10 months because using a case was too bulky for me. In the end the problem was that the GPS on it was wonky ever since 4.4.2~, and the camera always sucked indoors/lowlight situations (did fine outdoors in daylight).
I got the Note 4 for 2~ days, and found the camera to be excellent however during motion shots in okay to low lighting it would blur no matter what mode I used. Useless when capturing special moments with my loved ones and friends.
I will say battery life on the note 4 was EXCELLENT. Easily giving me 40%-60% battery life at the end of the day.
Unfortunately the note 4 can suffer in some intensive games, specially if they are not optimized for it.
I haven't seen any reviews use real life pictures with the S6/S6E in situations where there is a lot of movement in good to low light indoor situations (and low light outdoor situations), which is where the note 4 failed badly (and review sites kept favoring sun-lit categories over indoor photography to make assessments of picture taking with the Note 4).
Imho I'd wait for more people to get hands on with the devices before making judgement. Note 4 has better battery life, bigger screen, plus unbeatable s-pen. S6 has potentially better camera lens, potentially better UI, better speaker, better out of the box features (wireless charging, quicker charging, etc) and smaller footprint.