To be honest, I personally never understood this notion "of what Lisp should I choose?". For the first-timers, for learning - any Lisp would do, Clojure, Racket, Fennel, CL, Janet, even Emacs Lisp. Once you're through the basics - structural editing, REPL-driven workflow, etc., then switching between Lisps is not that difficult.

Yes, they are different languages, working atop different platforms. They have different semantics, vastly different core libraries, etc. Yet at the same time, somehow, there's little mental overhead when switching between them.

I don't have any difficulties moving between Fennel, Clojurescript, Clojure, Clojure-Dart, LFE. But if I had to manage writing code and maintain multiple projects in Lua, Javascript, Java, Erlang and Dart - I would claim that my name is Guy Stele Jr. and I am a very smart programmer. Alas, I'm not that smart, that's why I chose Lisp.