Even orkz and nids are smart in their own way. Both may prefer swarm tactics, but tend to mix up charges with bioplasma support (nids) or bombsquiggs and stikkbombs (orkz). Just having a group of orkboyz charge is kind of underplaying them. They have choppa, stikkbomb and gun, because while advancing, they keep firing nonstop at the enemy or throw grenades. Both are effectively disruptive, the one supresses, the other has people hightail it away from the nades and disrupts firing lines.