well, SBCL is 64bit, has native threads, can be built from another Lisp, the type inferencing is improved, the whole build process is totally painless. I can build a new SBCL in under a minute from scratch using the installed older SBCL. I can install it from Homebrew on my current Mac. It runs natively in 64bit on my M1 Pro Mac. I also like the Unicode support better in SBCL.
