Isn't that a bit of hyperbole? A device not working the way you expect doesn't mean it's not a working gadget. My car still works even if the A/C isn't as cold as I think it should be, for example.
And anyways, what makes you so sure that having 3GB of RAM fixes performance problems?
"True multitasking" is no excuse. The amount of memory in use does not necessarily change much just because more than one app is actively being used.
Seeing as you're justifying potential issues you could face on the Note 4, you should probably go ahead and get it regardless of how much RAM the iPhone 6 has. It doesn't seem like you've ever been happy with the iPhone.
To be clear, I'm not trying to say the Note 4 is a subpar device. But one issue being fixed (tab reloading) may not make up for other issues you could face. No device is perfect. But at the end of the day, all that matters is if it works for you.