More microphones result in better sound quality and enable the device to filter out background noise.
Parrot Zik Sport: 8
16. cable length
A long cable ensures more freedom of movement.
Pioneer SE-A1000: 6m
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.
Bang & Olufsen Beoplay H2
Beats by Dre Mixr
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.