What do you mean by effective, more effective at killing people, or more effective at pleasing the crowd? Gladiatorial combat was about pleasing the crowd and not necessarily about killing people, it was about a display of skill and courage and killing people was a side-effect/result of the match.

There were a significant variety of gladiators however a few types composed the vast majority of combatants, types such as the murmillo, thraex, hoplomachus, retarius, and the secutor. Many of the types of gladiators fought mainly another few specific types, so the secutor fought mainly the retarius as they had very different arms and armour which led to a fight determined by the skill of each combatant rather than a superiority in arms. If the style was effective, it pleased the crowd.

The crowd, as may be imagined, was the leading actor in these bloody dramas.

An interesting source on the roman games (I would high suggest you read it, it is not dry or boring): Cruelty and Civilization: The Roman Games by Roland Auguet