A straight plug is better when the jack is on the top or bottom of your player.
50% have it
16. has a 3.5mm male connector
A standard 3.5mm male connector is suitable for use with all MP3 players and computer sound cards.
83% 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.
23% have it
18. has a noise canceling microphone
These microphones are designed to filter out background noise from the desired sound. Especially useful in noisy environments.