The device's battery life (when in use) as given by the manufacturer. With a longer battery life you have to charge the device less often.
Sennheiser PXC 480: 50h
17. has an on-ear form
This device comfortably rests on top of your outer ears. As it doesn't block out everything from the outside world, it's preferred in places like office environments and recommended for outdoor activities.
Philips Fidelio NC1
22% have it
18. has a coiled cord
A coiled cord typically offers more flexibility as it can be extended, and taken outside for example.