I know this sounds weird...
I prefer the glass ones. Although they are more expensive it seems as if the water doesn't evaporate as quickly and the eggs can breath a little better. I have also found that some of my frogs prefer glass to plastic. I am not the only one who has noticed this.
I use film canisters for my thumbnails, but for everyone else I use glass petri dishes.
Another nice thing, you can bleach them and toss them in the diswasher without worring about bleach getting absorbed into the glass.
Another nice thing, the glass ones are very sturdy and have higher lips so eggs don't slide off easily.