With the ever growing list of supported AI models in Github Copilot, there is one question that is getting harder to answer.
Which model should I use?
You can try to safe some money and stay away from the premium request models, but even then you have a lot of options to choose from. You also could check out the model recommendations based on the task you try to achieve but isn’t there a better way?

Enter Auto mode
With the latest update of GitHub Copilot in Visual Studio Code now a new Auto option is available. When you select Auto from the model picker, Copilot will select an appropriate model for you.

It is not clear what criteria are used to select a model but you can find out the chosen model at the bottom of the response:
Be aware that it is be possible that Auto mode could choose a premium request model, although a discount of 10% is applied when auto mode selects a premium requests model (if you are using a paid plan).
For example, Sonnet 4 would be billed at .9x rather than 1x when using auto model selection.
Remark: Auto mode will only use premium request models with a maximum multiplier of 1.
More information
Auto model selection for Copilot in VS Code in public preview - GitHub Changelog
Supported AI models in GitHub Copilot - GitHub Docs
