Why Data and Voice is better in some App than others?

Dear Experts.

Using 4G data, Voice call on Weechat App is very good, better than Viber, Whatapp. Why?

Does Core network define QCI based on App?

Or Weechat software for Voice coding is better?

What do you mean “better”?

Do you have MOS measures?

Better voice quality.

No, it’s from my feeling - but also many people feel like this.

Mute call perspective is also good.

At least from the human ear detectable mute even though there is no MOS or mute score.

Some apps require more bandwidth than others
Echo cancellation and noise reduction in various apps
Processing power
Hardware and software
Network connectivity

Can you give detail kpi requirement for some apps in voice call?