From Command and Conquer Wiki

The Cabal Obelisk was comparable to a regular Nod Obelisk of Light in terms of raw power and range, but possessed several other advantages.

Its primary advantage was the ability to shoot through the Firestorm walls that Cabal was fond of using to defend his core, thus allowing Cabal to keep meddlers away from his core. In the event that his core was breached, the Cabal obelisk was designed to be a formidable defense, roughly twice as resilient against enemy attacks as a regular Obelisk of Light, and having a shorter cooldown time as well. However, it was nowhere near as effective a defense as the Core Defender, upon whose massive shoulders the final defense of the core truly rested.

When GDI and Nod forces launched their final attack against Cabal's core, one of the things they did was to destroy the only working prototype of this technology.