1. Much quieter and faster when focusing because USM autofocus. 2. Slightly faster 3. Bayonet made of metal and not plastic, which means less wear and tear and a more accurate back focus 4. More valuable feeling 5. Both have the disadvantage that the lens changes its length when focusing. 6. With both, there should be no pressure on the lens barrel, so always leave the lens hood in the working position. 7. Both offer good value for money. 8. Haven't regretted the change.