I think its speed and punch resistance, especially to the body. Speed is great but it can't be relied on later on in the career. Kahn is a case in point, Ryan Garcia is a future case in point. Punch resistance to the body - look at Golovkin.
I'm gonna go out on a limb here and say ugas was too tall. All of Manny s flurries or combos were basically missing the mark by hovering around below 3 to 4 (maybe more) inches of ugas head. He didn't dare punch upwards because he a didn't train for that b he would lose power. Ugass head was safe out of distance. Not to mention he had a piston like jab and a beautiful right hand cross/ straight that he cranked like an mfer. He simply fought tall, had good defense, and was essentially using the right game plan. He put up a boxing lesson.