I was in your same situation a month back lost as to what to get......then I came to know that the S6 has a smaller battery capacity than even the S5 despite it having higher specs, better camera, so I bought the Note 4.
- Note 4 has a 3200 mAH battery, you can use it for 2 days easily on a single charge
- Note 4 has a better camera, even though they're both 16MP, just take a look at the 2nd page in this camera shootout and look at the red carpet on the balcony, on the S6, it lacks details, you can't see the yellow lines in the red carpet, the Note 4's lens is better:
Intergalactic camera shootout: Galaxy S6 vs. Galaxy S5 vs. Note 4 vs. iPhone 6 - GSMArena.com
- Note 4 has expandable memory, so it turns out much cheaper if you just add a 128GB SD card later when you need more storage space. With the S6, going for the 128GB will drill a hole in your pocket as it's very expensive
- Note 4 has a bigger screen, a pleasure to browse the web and view apps with more screen real estate