Actually, you're wrong. I had a Galaxy S2 Skyrocket with 4.1.2 and it ran fine, though the screen resolution was lower newer SoCs would run fine with 1GB RAM even with a 720p display, which is about comparable to the iPhone 6 given the Skyrocket's screen is only 4.5" vs 4.7" on the i6. It had, literally, no performance issues.
Yes, there are people whose phones are cruddy and run like crap. Then again, there are people with iPhones who overload their phonesand end up with tons of performance issues. That Skyrocket ran fine 2+ years after release. It would run even better if it had a current SoC and Android 4.4+ on it. I have no doubts. All that, with 1GB RAM and TouchWiz 4.0/Nature UX, which was even WORSE than the newer, more optimized, variant of TouchWiz.
The reason why a lot of low end Android devices run like crap is not just cause the RAM is low:
1. In developing markets, OEMs often use low end SoCs that simply can't hold a candle to Qualcomm's high end SoCs used in flagships. This is no different than a PC. A PC with an old/slow processor with 8GB RAM still won't play Crysis. RAM can only take you so far, and it cannot eliminate I/O or Processing Bottlenecks in the device.
2. Lower end devices often use SoCs like a Snapdragon 400 when they use QC, while flagships are using Snapdragon 800-series SoCs which perform much better. See above.
3. You're mentioning only RAM Size, but not paying any attention to other factors that determine performance, like ram SPEED (low end devices often use slower ram chips), the type of storage and the speed of the storage (EMC vs. fast NAND Flash). Again, See #1. In fact, we seen how much the storage type can affect performance back in 2010 when Samsung released a Samsung Focus Windows Phone with NAND Flash Storage and HTC Introduced the HD7 with EMC. The Focus outperformed it, noticeably, even though every other spec was largely equivalent (Same SoC, Same RAM Size, Same Screen Resolution, Same GPU, etc.).
Phones like the Moto G have shown that Android can fly on 1GB RAM, and many mainstream Android devices have stuck with 2GB and run just fine despite some models going with 3GB. In many cases, going with MORE RAM *can* hurt more than it helps, as the OS will use that RAM as a cache and background processes will run longer before being tethered the system, meaning CPU Efficiency (due to higher levels of multi-tasking) and Battery May be adversely affected. This is why Apple and Microsoft have enacted the methods they do to curtail background processing in their OSes.
As far as the display PPI. You seem to be content with ignorance, as you haven't even bothered to digest the very valid points that I've put forth in my post above.
A 720p Super AMOLED Screen is less sharp than a 720p LCD Screen due to differences in subpixel arrangement. Going above 1080p helps Samsung more on a Super AMOLED display than it helps LG or Apple on their LCDs. On the Note 3's 1080p display (386 PPI), you can clearly see that it is less sharp than the Note 4's QHD display. Yes, if you're looking from afar you may not notice it as much, but it doesn't change the fact that the bump in resolution is clearly there, and clearly obvious, and it's not like they're going to invent their own aspect ratio just not to make it as "big" a jump so you don't criticize them for overspeccing their display... ...
You're assuming that everything Samsung does is in reaction to what competitors are doing, rather than them simply improving the quality of their product's display experience.
And still, the Note 4's display is better than the 6 Plus. I just bought the 6 Plus, and owning it won't change the facts. The display is simply not as good as Samsung's.
And these phones won't get 9-10 hours of "screen on time," which is the generally accepted method for measuring runtime under average/moderate use. It's not like you'll be instagramming with your screen off, you know...
Yes, if you count listening to Music with the screen off as "use" it will go much further than 10 hours. Even a Galaxy S Vibrant from 2010 will go 30+ hours playing music like that. Once you start using the device with the screen on, battery drain accelerates astronomically.