I feel they are different and present the bait in a different ways. The stray line rig presents a bait in a much more natural fashion, allowing it to drift around more in the water column... Although on a surf beach it can be pushed around by the currents. I use a unweighted strayline for targeting Snapper in sheltered waters where distance casts are not required.
The pulley rig is good for distance, plus allowing a degree of slack so less likely to spook a fish the moment it grabs the bait.
The ledger rig can present multiple baits and its good if you want to try and keep the bait off the bottom and maybe cover more of the water column.