I've used it all (plastic, stainless steel, ceramic) and my favorite was the ceramic for the cleaning factor and the look but then Ellie's dishes started to smell really odd even after bleaching.
They were made in China and I was a bit nervous about what could be doing that. So, we went to Pyrex glass. They are really cute and made in the USA! My only concern is that they may chip and I don't want her to get cut but the ceramic ones chip too. So far these are the ones I am most comfortable with. I might get a stand for them and just set them inside the dishes that come with the stand. The are also small and easily washable, so I have 4 of them and rotate.