These two Cinnamomum oils belong to laural family. They have shown inhibition of the COX 2, enzyme. The result of this specificity is reduction of discomfort and inflammation without inhibiting COX 1, the enzyme responsible for the mucous secretion in the stomach. Most pain relievers inhibit both enzymes, the level of inhibition differing between specific drugs, such as Aleve, Naproxen, Aspirin and other NSAIDs. Inhibiting Cox 1 enzyme has the side effect of stomach irritation and an increased risk for gastric ulcerations due to the decreased secretion of mucus.

Other Properties of the two Cinnamomum Oils:

Cassia prevents microbial and fungal growth and supports healthy circulation.

Cinnamon Bark also prevents various forms of microbes and parasites from inhabiting our bodies. It is circulatory and digestive supporting.

References:
Essential Oils Desk Reference, Essential Science Publishing