Hi North Star
There are huge differences in diffusers. The real cheap ones like those sold in aquarium stores are truly toxic when used with ozone. Most of them are glued together with glues which break down with ozone. In fact the entire diffuser will disintegrate over time. Most of them are glued ceramic material. When you use them in oils, the decomposition of the diffuser takes less than a week if high ozone concentrations are used.
However, there are other diffusers made of real stone that are very ozone resistant. These diffusers are actually made of silica bonded by heat and pressure to form the stone. The best ones have the hose barbs attached with silicone.
Although glass and stainless steel are definitely the best diffusers because they are ozone proof, the heat pressed silica ones IMHO are a much less expensive and acceptable choice.
hope this helps