Although Kiu Fung and Kau Mor Tze never fought during DGSD, it is generally believed that these two martial artists were at about the same level of prowess.
Kau Mor Tze visited the Heavenly Dragon Temple in Dali and embarrassed the monks there by besting them in single combat. Even when the six senior monks (or five monks plus a disguised Deun Jing Ming) joined forces and used their 6 Mak Divine Swords against him, Kau Mor Tze was able to battle them to a standstill.
Kiu Fung once confided in Ah Chu that he didn't have confidence in his ability to defeat a 6 Mak Divine Swords user. Coming from Kiu Fung, that's a stunning revelation: he seldom lacks confidence in his abilities against any opponent...or any martial art. 6 Mak Divine Swords, however, had Kiu Fung spooked.
Although Kau Mor Tze and Kiu Fung were at the same level of martial arts, their techniques differed. Kau Mor Tze used a kind of chop suey martial art made from bits and pieces of Shaolin and Siu Yiu Sect techniques. Kiu Fung, on the other hand, used proper Shaolin techniques and Hong Lung 28 Palms. Do you think Kiu Fung would have done at least as well (if not better) against the 6 Mak Divine Sword-using monks at Heavenly Dragon Temple as Kau Mor Tze did?