To repeat the point made by Stavros:
To compare Maxima properly one needs to have two different Lisp
implementations, one using 32 bits (for addresses) and one using 64 bits.
Perhaps there is a working 64-bit SBCL as well as a 32-bit one. This will
require 2 Maxima binaries.
Taking the same binary and running it with the OS in 32 or 64 bit mode is
not such an interesting test because a 32-bit lisp implementation will not
use any 64-bit operations, and so could hardly benefit.
RJF