While it is unknown the exact number of Covenant ships that were built, they likely had thousands, which were all more powerful than an equivalent sized UNSC ship.
ALL COVENANT WARSHIPS
Though not all Covenant ships were larger than UNSC ships, many were, including ships like the mile-long CCS-class battlecruiser, the three-mile long CAS-class assault carrier, and the eighteen-mile long CSO-class supercarrier. This advantage in size was coupled with superior weaponry and shielding technology, which made a Covenant vessel impossible to destroy without sustained fire or advanced tactics. At the end of the Human-Covenant War, much of the fleet was destroyed, either by the UNSC on Earth, or mostly by self-immolation during the Great Schism. Several ships, including the Pious Inquisitor, were were sold on the black market, requiring ONI and UNSC intervention to stop these weapons of mass destruction for getting into the hands of terrorists.