This topic is done and beaten to death every time android or apple release a major OS revision.
However, i do think its misleading and in the case of android, downright wrong.
The reason i left Apple was the software changes. IOS updates crippled my (3GS) iphone and didn't offer all of the updated software to the older phones So IOS isn't perfect. My partner simply refuses to update her Iphone regardless. She's has experience of the Lag and issues.
This idea that Iphones get updates longer than android isn't completely true either. Yes, Most android phone has two full updates, but Android has shifted most of the core functionality to GPS and security patches. These carry on much longer than the two years.
and what of the updates? Android has pretty much all the functionality it can give. There is no update required to give the user cut and paste or drag and drop. Much of the stuff apple update can be done on android using a apk. these days, for IOS and Android, updates are just window dressing.
Updates on IOS are used as a blazing beacon by apple fans to kick android but in reality, i don't think there is much in it.
How Android updates is a different matter and is a mess and google should clean the process up properly. I won't hold breath on that. As a software company, they seem to be getting worse and worse.
For the note 5, do a full factory reset, set up as new (No recovery or backups) and clear your cache. Shoudl be back to being zippy