First, you can install the full framework into any project, not just new ones: tempestphp.com/framework/01-getting-started#content-tempest-as-a-package
Second, Tempest has an (almost) no-config design. Developers should focus on writing code, not config. For rare cases that need configuration (like database setup), you'll work with properly config objects instead of arrays or yaml files. Autocompletion everywhere 🔥
Next: Tempest embraces attributes. There's little to say about that besides that it's awesome once you're used to it.
Then, the biggest one: discovery. Tempest will scan your code for you. No more manual defining of routes, event listeners, console commands, and what not. Everything is automated. You just start writing code.
tempestphp.com/internals/02-discovery
Finally there are initializers (which are discovered as well). This is how you manage container definitions in Tempest, super clean: