Look, I've played every Halo except for 5, because it's not out. Master Chief needs to pick up abilities and grenades to use them, Guardians don't. Master Chief has no actual abilities other than his strength and reaction time, but those don't come into play in the game much at all and wouldn't assist him much against a Guardian. Without his armor and weapons, he surmounts to nothing because those can be stripped away. As for a Guardian, the Light isn't removable, they don't need weapons to be strong because they'll always have their abilities.