Was a kind of "loaded" question to begin with but OP probably didn't know about it. Generally, Common and Scheme lispers are like PC and Apple computer "people", they don't mix. Which one is best is probably not as relevant as which one "works" for you. Really, there is not that much difference. Likely a preference for one over the other maybe influenced by which one you learn first. (To me, an empty list should be "nothing", known in CL as NIL, and that makes me a Common Lisper.) I like the integration of SBCL with Slime using EMACS, but SBCL is not for everyone. For one thing, SBCL is very strict. If you just want to "have fun" the GNU clisp is easy and available for virtually every platform.
