> I don't know the actual performance of commercial Lisps like Allegro Common Lisp and LispWorks, but I imagine it is quite good, given that they stay in busine

> I don't know the actual performance of commercial Lisps like Allegro Common Lisp and LispWorks, but I imagine it is quite good, given that they stay in business. Performance is not one easy number. Applications have different performance requirements. In many benchmarks for typed or type inferred code SBCL tends to be slightly faster with less programming effort. Fast can mean for example: * fastest possible execution of optimized code Then one might not care about code size, code safety, robustness, threading capability, interrupts, . * fast execution of non-optimized robust, flexible, reflective, debuggable code. Allegro CL and LispWorks integrate a lot of features. These features are provided over some amount of platforms, with only few restrictions. They provide relatively good performance of a native code compiler. Some robustness is needed for commercial applications, thus I would expect an advantage there.