As an owner of both an iPhone 6 plus and a Note 4, I can say that you will immediately notice the battery life difference. If I leave my Note 4 on a table for a day and don't touch it, it will drop to 50% battery without me actually using it. The iPhone in the same scenario will lose maybe 10% tops.
The iPhone 6+ is also much, much, much faster to use than the Note 4. No lag, no waiting for stuff to open, no having to re-launch apps when all you did is switch away to check your email.
I detest my Note 4 because it's slower and gets worse battery life than the HTC One M7 it replaced. And we're talking about a device that's two generations newer.
Sure, it runs games at a higher frame rate compared to the M7 but when the OS lags to hell when doing something simple like opening a web page, I just don't care.
What annoys me is that Android as an OS is lovely. It's just companies like Samsung that are ruining the experience and putting people off.