There is no best bitrate, only the right bitrate.
The right bitrate for a file depends on what you want to use that file for and the means of delivering the audio. In general, a high bitrate means high-quality audio, provided the sample rate and bit depth are also high. More information, in a very general sense, means better sound quality.
Audio CD bitrate is always 1,411 kilobits per second (Kbps). The MP3 format can range from around 96 to 320Kbps, and streaming services like Spotify range from around 96 to 160Kbps.
High bitrates appeal to audiophiles, but they are not always better. Keep in mind how your digital audio is going to have to contend with bottlenecks. If listeners will be downloading it or listening to it on physical audio formats, you can afford a high bitrate. If they’re streaming it, you likely want the bitrate to be a bit lower so it can be streamed effectively. However, below about 90Kbps the human ear will notice a significant drop in quality, even without training.
Also, a high-bitrate and high-fidelity file does not matter if it’s not delivered on quality hardware. If users are listening to your audio on mass-market earbuds or headphones, they will not be able to get everything that high-fidelity audio offers anyway. CD-quality bitrate, which is high, sounds its best on a professional stereo system that is able to adequately express the very high and very low frequencies 1,411Kbps is able to accommodate. Most earbuds, and many desktop speakers, will not be able to express those frequencies.
Finding the right bitrate.
When you’re starting a new audio project, it’s good to record the best quality you possibly can, with a high sample rate and bit depth. When producing audio, you need to keep in mind how your listener will be interacting with your audio. Variable bit rate can become useful when looking at the amount of details needed, as it continuously changes bit rate throughout playback.
Regardless, if you’re creating audio of any kind you should always keep your highest-quality files around to future-proof against new technology. Future audio formats could require greater bitrates, and future connections or hardware could potentially deliver high-fidelity audio. It’s entirely possible that commercial audio hardware in the next decade or so will be able to express bitrates greater than 160Kbps, so keep your old uncompressed files. It’s always possible to convert uncompressed files into a new format.
Knowing what type of files to use is only one part of audio production. Learning how to work with a graphic equalizer and understanding how to mix music will greatly improve the audio you produce, whatever the bitrate.