We get asked this question alot and over the time I have been running the salt and pepper mills plus site my answer has got more elaborate!

First, if you compare the mechanism alone:
Ceramic pepper mills are probably harder wearing and more comfortable with damp peppercorns. However, stainless steel mechanisms such as PEUGEOT have specifically designed for the task of grinding pepper, and I think probably work better.

Second, you need to compare the specific brand of ceramic mills.
These really do vary. I would say that CrushGrind ceramic pepper mills are amongst the best and have added advantages like no spindle, so they are easy to refill. If you compared a CrushGrind to a bog standard stainless steel grinder, I would recommend the CrushGrind. But the PEUGEOT pepper grinder, which is stainless steel, I think is better than the CrushGrind.

Third, you do need to think about the mill body as well as the mechanism.
A big reason why I now recommend PEUGEOT mills above all others ( and at first I was more circumspect) is that I think that the quality of the materials and manufacture in the mill body is second to none. I have fewer returns of any kind on PEUGEOT than on any other mill brand. That speaks for itself.

Fourth, you need to consider the quality of the manfacturing process.
Ceramic mills are a new technology and in many ways really extremely good and welcome. It is great that your standard ceramic salt mill will grind a wet sea salt., for example. Stainless steel just cannot match that. However, because they are new technology, I would say that the quality is more variable and whilst the manufacturers are extremely good at replacing faulty mills (I have never had them question a returned item), you have to say that having quality control sorted out first of all would be a bonus.

Hope this helps

Claire