from what i understand the notched pulley was first generation. smooth grooves were second generation. no diff. in performance
the notched pulleys were shredding belts in the beginning from the sharp edges. as the pulley wore in it became a non issue but the smooth pulley was built to fix it
this is a great buy!!!! if i didnt already have a c3 and 2 oem pulleys and 2 spare bearings i would be all over this!