Fit decides the sound
An in-ear seal and a headband clamp change bass and comfort. A cheaper pair that fits well can be better than an expensive pair that does not.
Noise cancelling is not one feature
Active noise cancelling works best on low-frequency sounds; it is not a substitute for passive isolation. Check the transparency mode and the microphone quality for calls.
Codecs and platform support
High-quality codecs need support on both the headphones and the phone. Check the Bluetooth version, multipoint pairing and whether a wired connection is available.
Battery and repairability
Battery life falls with age, and many earbuds are not repairable. Check the battery warranty and whether replacement parts are available.
Try before buying
Comfort and fit are personal. Buy from a retailer with a return policy and test the headphones on your own devices.