That two protocols are used by Selenium WebDriver to interact with browser drivers as below:
As browser vendors update to support W3C WebDriver protocol and shift away from JSON Wire Protocol (JWP), this can bring increased stability in your Selenium tests across different browsers.
Some browsers has stopped to support JWP in latest version, like Safari. And others may will do so in the future.
That means, we need to migrate our WebDriver tests to use w3c standards ASAP.
For BrowserStacks Selenium users, have a look this guide: https://www.browserstack.com/automate/selenium-4
For SourceLabs Selenium users, read this: https://docs.saucelabs.com/dev/w3c-webdriver-capabilities/index.html