1. Key difference between @babel/cli and babel-cli: The primary difference between @babel/cli and babel-cli is the way they are installed and used.
2. Installation process difference: To install @babel/cli, you can use NPM and run the command npm install @babel/cli. On the other hand, babel-cli can be installed using the command npm install --global babel-cli.
3. Command line interface difference: When using @babel/cli, the command to transpile a file is npx babel <source-file> --out-file <output-file>. Whereas, when using babel-cli, the command is babel <source-file> --out-file <output-file>.
4. Package and plugin architecture difference: In @babel/cli, the packages and plugins are organized under the @babel scope and can be installed as @babel/preset-env or @babel/plugin-transform-classes using NPM. On the other hand, babel-cli uses the babel-preset-env or babel-plugin-transform-classes package names for installation.
5. Configuration file difference: @babel/cli uses a .babelrc file or its equivalent in package.json to store the Babel configuration options. In contrast, babel-cli uses a .babelrc file or a babel.config.js file to store the configuration options.
6. Default output directory difference: When transpiling files using @babel/cli, the output is saved in the same directory as the source file by default. However, babel-cli saves the transpiled output in the current working directory by default.

In summary, the key differences between @babel/cli and babel-cli include differences in installation process, command line interface, package and plugin architecture, configuration file, and default output directory.