The main difference is the License of Ghostscript, which does the actual conversion of the printer data into PDF. The AFPL (Aladdin Free Public License) release normally is the most recent version and a little better than the GPL /GNU General Public License). So the AFPL is the best choice and does not restrict normal users any more than the GPL release. But there are some special cases where the GPL may be required and for this there is this second release.