All grimoire cards suggest otherwise. They appear to come from large cocoons and then gradually morph into the forms we see in-game. So I'd say they are more like sophisticated bipedal Zerg from Starcraft. That and their god tier entities like Crota can apparently will entire netherworld into existence, which is something the flood could never do. In short the flood are animals in comparison while the hive are a sentient race that have basically become one with the darkness that they worship.