I've never used Chicken Scheme (only Racket), but I've read a few articles about it and the advantages seem to be:

-Compiles to C, so it's highly portable and you get the performance optimization benefits of whichever C compiler you're using

-Lots of libraries

-Good packaging system, with packages that are cutely referred to as "eggs" (similar to Ruby's "gems" system)

Racket is great too, though, and DrRacket is an excellent IDE with minimal install/configuration difficulty. It just works.

I'm not really sure what tools exist for Chicken Scheme. With Clojure, you're probably going to need to configure emacs or another text editor for syntax highlighting and REPL. I write Clojure in Sublime Text 2 with SublimeREPL but that requires some config and isn't technically free. There are Eclipse and NetBeans plugins, but I dislike Java IDEs for their enormous memory footprint.