I previously had a 6 Plus on order for October 3 delivery but cancelled after using it in person. The Note 4 seems a much better deal being 0.2 inches shorter while having a screen 0.2 in larger and higher ppi. Any size savings help with pocketability, the huge top bezel on iPhones need to go.
The advantage of removable battery and expandable storage is obvious. It's annoying that the iPhone is stuck at 16gb as a minimum, which really isn't useable if you use your phone for more than calls and browsing. That makes the Note $150 cheaper at $700 vs $850 iPhone 64gb.
I was also annoyed at Apple sticking with 1gb RAM which means the phone won't handle split screen multitasking well (supposedly coming n IOS 8.1) and results in a sub par browser experience. For current Android phones I don't remember my tabs ever refreshing, while with Safari it happens all the time (but not as badly in IOS 8).
The big downside to the Note 4 is Samsung bloatware. However, Android phones are generally hacked rapidly so using a custom ROM with only S pen apps intact should be easy to do.
The s pen should hopefully be useful to take notes at conferences/lectures although the screen might be too small do that effectively?