DERBY NOTES (4/24-25): 'Spell' to Oaks only..

Is there really that big a difference between dirt and synthetic surfaces?? I have walked the tracks at Turfway and Keeneland and they seem predominately dirt with carpet and tire fragments mixed in. Obviously these substances would lessen the concussive shock but they still seem pretty similar to a dirt surface in terms of footing. Big Brown 5F in 58. Pretty fast but Hard Spun worked 5F in 57 last year and ran a bang up race. Was BB ridden by a jockey or a larger ex rider???