More microphones result in better sound quality and enable the device to filter out background noise.
Parrot Zik Sport: 8
16. has a coiled cord
A coiled cord typically offers more flexibility as it can be extended, and taken outside for example.
Bang & Olufsen Beoplay H2
Beats by Dre Mixr
8% have it
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.