Well, Elemental Attack is bad enough as it is (Magic x 2)P DV and -Magic AP, where Magic = Spirit Force. So a Force 6 spirit has 12P, -6 AP base + hits. The toxic spirits have the additional advantage of bypassing armor with their toxic attacks, so they are that much more lethal. As a Hermetic, you have Fire spirits as your combat type, and they have Elemental Attack, so they can really make for a bad day for whoever you point them towards. But, yeah, toxic spirits are slightly stronger, hence the lure of the dark side. Shamans get Beast spirits as their Combat spirit, which are horribly ineffective by comparison (no notable attack ability by default, Natural Weapons as an optional power which is only Magic P DV with no AP).