1. My current Note 3 is as fast/faster than my wife's 5S on most tasks. I have no doubt that Note 4 will not be any slower than iPhone 6/6 Plus. Days of iPhone being noticeably snappier are well past us on modern hardware.
2. While theoretically you are right, in practice it's a non-issue. This isn't Windows vs OS X.
3. That's actually my biggest concern with the 6 Plus - how will the battery life compare to Note 3/4. My Note is a batter monster, easily lasting a couple of days if I'm not using it non-stop. My wife has to keep charging her 5S more often, while not using it as much.
4. I'm sold on the concept, as Google Wallet has been a major fail so far. Let's hope Apple Pay works as advertised.
My list of pros/cons, and why I ended up ordering 6 Plus:
Android Phablet Pros
1. Battery life, including ability to carry extra one (to be seen how 6 Plus performs)
2. RAM - I'm a heavy Chrome on Android user, and Note 3 is great in that respect. My wife's iPad Mini with Retina (yes, she's Apple all the way!) reloads tabs to a point that I get frustrated any time I sit down with it, and end up surfing on my Note 3.
3. S-Pen - I'm not a fanatic, but I do use it occasionally, as it comes in handy for PDF annotation, and quick notes, etc. I'll miss it at those times.
4. Kindle app - I read a ton of books on my phone, and being able to purchase books straight from the app is just convenient. Not a deal breaker, but one of those things that can annoy on iOS.
iPhone Phablet Pros
1. iOS - iOS 8 looks great, and is still the best mobile OS on the planet. 2nd biggest reason for me to be back to Apple.
2. Camera - really looking forward to high-quality optics, great slow-mo, and overall photo/video handling.
3. iMessage - it's probably the biggest day-to-day item I've been missing since giving up an iPhone. There is just no better messaging ecosystem IMHO.
4. LCD screen - Since I read a lot of books, and good portion of that time is in bed, an LCD screen is better since it can be dimmed better than the SuperAMOLED on my Note 3. Probably my biggest pet peeve with the Note.
Looking forward to using an iPhone sized for my needs!