You can feel the tiniest, itsy bitsiest difference. I've got the AEM pulley kit. I gave a someone a pack of cigarettes and 10 bucks to do one of them. Me and a friend did the other. Wasn't too hard at all.

My friend got the 'ebay special'... but we had to go back and forth to autozone to find the right belt sizes. Good thing about the AEM kit, was that it came with the belts.