An L-shaped plug is better if the jack is on the left or right side of the device, so that the cable isn't bent, and is less likely to break when the device is in your pocket.
31% have it
16. has a straight plug
A straight plug is better when the jack is on the top or bottom of your player.
50% have it
17. has a 3.5mm male connector
A standard 3.5mm male connector is suitable for use with all MP3 players and computer sound cards.
82% have it
18. number of microphones
More microphones result in better sound quality and enable the device to filter out background noise.
Parrot Zik Sport: 8
19. sweat resistant
Resistance to sweat makes it ideal for use while doing sports.
13% have it
20. cable length
A long cable ensures more freedom of movement.
Pioneer SE-A1000: 6m
21. 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.
23% have it
22. has an earbud form
The earbud form is ultracompact and lightweight, with little or no interference with earrings, spectacles, hats, or hairstyles. For some people it is more comfortable than in-ear form.