Flogging this to death but, the 6+ is too slippy without a case and fatter with one. Yes, there are skins but there remains the lack of flexibility in iOS to freely place icons (ie. use the lower half of the screen only). Reachability feels last-minute and is un-Apple in that it adds steps to a process instead of simplifying things.
Whilst the Note isn't perfect, that it tapers to the band, which is about 5-6mm, makes it feel much thinner than the advertised depth - my natural grip means I only feel the sides given the gap between my hands and the back of the phone. The 6+ could arc to a thicker depth and it would still feel the same to me. Ergonomically, the 3G was the iPhone's high point.
Still, I doubt the big head and chin are disappearing soon. Nor the bezels, or free icon placement, or the ability to show useful information in the upper area instead of hiding it away in the (unreachable) top pull-down. iOS works on the 6 but is a flawed mismatch on the 6+ hardware so I'm hoping for big things in iOS9 as I'd like to pick up a 6S with 2GB RAM (for future proofing).
The note 4 is thicker and heavier though, also has sharp edges, cases don't suit on the note anyway as they can scratch the paint off the sides, Black version I have read, is it right the White versions edges are not painted?
Tapering makes a big difference to me at least. Edges are firm and grippy but some may find the too aggressive. My paint (black) version is as new and, after trying cases for two months, which includes taking it off and recasting every other day to change batteries, there's no sign of case rub.
To each his own but I've concluded cases only make phones bigger, thicker, uglier, and more difficult to handle. So, I prefer something grippy.