Planned obsolesence is real. No matter how much Apple fanboys deny it.
Apple will PURPOSELY leave 1 or 2 animations stuttery or laggy for devices 1 generation older.
For example,
1) iPad Air 1 was flawless on iOS 7. But when iOS 8 came out, it started to stutter in Safari when keyboard was brought up. Safari was really painful to use.
2) Now iPad Air 2 was also flawless on iOS 8 throughout. People even joked that it's ridiculously overpowered for the software that runs it. But then came iOS 9! It caused stutter on it during multitasking animation.
So there will always be that 1 magical animation somewhere which will lag, stutter or do both.
Apple is not trying to be obvious with their approach, but that is enough to convince people which is the better product during side by side comparison in the store. People are already on the fence leaning towards the upgrade to a newer device. This provices just the right amount of nudge to tip the scales in Apple's favor.
I openly challenge all Apple fanboys here to prove to me that the above 2 scenarios are false and are some figment of my imagination.