Aside from the differences you mentioned, the XS version should be somewhat faster, or perhaps consume less memory.
XS stands for eXternal Subroutine, and is a method for writing perl functions in C. This is used extensively to either tie existing C libraries to perl, or to write more efficient or faster functions.

PerlXS is the documentation page on XS if you are interested.

Generally module names containing XS denote that some or all of the module is in fact written in C. I am making the assumption that because you asked what other reasons there are for using the XS version, you didn't know this. My apologies if I am incorrect.