I love Racket. It's a broad ecosystem of endless libraries, good documentation, and everyone rowing the boat in the same direction.
But Common Lisp. Performance is important to the Common Lisp community. It has been from the beginning long long ago.
Now, from a user perspective I think you should probably refrain from jumping onto a language based on potential performance. Common Lisp is a huge language, and writing performant code will require you to know much about both the language and its tooling/implementation. By comparison, Racket is simpler to jump into, if only because the core language is much smaller (the macro system on the other hand, is more complex). So it all depends what you're expecting from the experience: learning? having fun? becoming an expert?
I don't know Guile, but obviously it's going to be closer to Racket than Common Lisp.
I still recommend you evaluate them both, but people's time being limited I can see why you might not.