Allegro and Lispworks are proprietary with product support provided by the vendors, SBCL and Clozure are opensource. Allegro and Lispworks have their own IDEs a

Allegro and Lispworks are proprietary with product support provided by the vendors, SBCL and Clozure are opensource. Allegro and Lispworks have their own IDEs and some proprietary libraries bundled in (e.g. CAPI which is probably the best option for cross-platform GUI for this language), while SBCL and Clozure both rely on SLIME and Quicklisp. SBCL produces fastest x86-64 machine code, as far as I know. Clozure has superior macOS support, as it used to be owned by Apple before they spun it off and was generally Mac-centric throughout its history.