The 2016 is Bluetooth LE, so it doesn’t require pairing before connection and in my experience connects way faster.
The data rate is higher at 256Hz, rather than 220Hz.
It has gyroscope and accelerometer at 52Hz, whereas the 2014 only had an accelerometer at 50Hz.
On the downside, it only has a single AUX/USB connection on the right ear.
Firmware wise, there are different presets available.