CD
The ring and Scotsman system needs chain to work, because you pull the rode then the chain through the ring, then, when the flukes hit the ring, the weight of the chain falling on the other side of the ring is more than that of the anchor, and it keeps the anchor trapped at the ring.
I used the anchor puller thing you mentioned first before, but I find the ring to be a more simple concept, nothing to get jammed, no problem dealing with spliced rodes, less to go wrong. I'm much happier with a ring and chain.