That one is more difficult to install and needs a cut across the top of the barrel to secure properly. (Supposedly it will still work without the cut, but mine popped loose within a few shots without the cut). The Dinzag one needs only a small dimple drilled in the barrel for the set screw to engage. Also, the Dinzag one prevents the handguard from riding up at the front, whereas the CSS one needs a little hack to prevent that. (Not difficult, though). I like the Dinzag one best, but the price for the other is compelling. $80 is too much for a handguard retainer.
what about the Bulgaria