64-bit LispWorks has a larger address space, subject to physical memory. The maximum heap sizes are shown in Default range for 64-bit LispWorks heap.
You can make larger arrays and the fixnum type is much larger than in 32-bit LispWorks. The values of various Common Lisp architectural constants reflect this, as shown in Architectural constants.
Other differences in 64-bit LispWorks are noted in the remaining sections of this chapter.
LispWorks User Guide and Reference Manual - 13 Feb 2015