4600s are for heavy towing
5100s are a bit softer. Made for both lifted AND stock height.
Had 4600s on last truck and 5100s on current truck. Prefer the 5100s as this truck is also a daily driver.
Either way can't really go wrong when compared to the **** stock shocks GM puts on these trucks. Three of mine were gone at 22k miles when I put on the bilsteins. I will never own another truck with factory shocks.