I do love me some imessage. I realized I don't sent much gifs anywho to make it a deal-breaker. I prefer a texting app like textra. The quick reply on the 6+ is cheeks I was hoping they'd make it similar to bitesms. Textra lets you send gifs.. but they're small and not full gifs that you can copy pasta like on the iPhones. One thing I hate about the 6+.. is Google lagging on updating YouTube.. that's like one of my goto apps and that thing is trash on there :x.. it lags going to landscape mode.. always pisses me off
As far as pros and cons I'll give my best shot.. do know I go back and forth between Android phones and iPhones randomly when I feel.
Battery: I'd say they're both pretty equal in terms of battery life. I think the standby time on the iPhone is better, but when you're using the phone I think the Note has a slight advantage.. battery doesn't fall as fast when I'm watching videos or browsing the web. Both devices should last you the whole day. You can give a slight advantage to the Note mainly due to it being user-replaceable. And they've got that quick charging technology which is pretty clutch when you need to charge before you head out.
Screen: If we're going off just the spec sheet the Note 4 wins.. but me personally I couldn't really tell the difference. Though I do prefer the colors on the Notes screen. This one is pretty close, but most displays out these days are great.
Speakers: I think they're both equally average. If I had to choose one it'd probably be the 6+ because it's on the bottom. I found my hands do cover them sometimes when I'm watching videos in landscape in my hands, same probably with the Note. I give it the edge cause when I lay it down and watch a video it still sounds normal.. the note sounds all jacked when it's laying down and the speakers are covered.
Camera: I can't pick a winner here they're both really good cameras. If you get a note make sure the camera doesn't have the autofocus problem.. if so return it for a new one. They're both gonna give you really good photos.. they both win here for me personally.
Build: The 6+ is thinner and lighter.. but does not feel very good in the hands without a case. The Note without a case feels great.. that back piece, though people complain, it makes the phones not slippery and feels awesome imo.
My verdict is at the end of the day you can't go wrong with either of these phones. They'll both have their pros and cons to different people, it's all personal preference at the end of the day. Go with what you like and don't let anyone say otherwise it's you using the phone that's all that matters.