I believe it is safe to say that you have to put in more work with the 6.5inch pads because the bigger pads tend to stop spinning on you much easier, which means you wont be correcting paint when the pc only jiggles and doesnt spin. I used 6.5 inch pads successfully when i ran out of 5.5 hydro tech pads, but man it is more work on your hands! It is definitely recommended that you get 5.5 to reap the benefits without spending so much time, not to mention you are already using a pc, so if you dont have patience and skill, the pc will be useless to you. You can get same results with both but its your call, i bought my pc with 6.5 pads only too lol..