I have read that Ceylon cinnamon is sweeter. It is also 3X the price. Is it really worth it?
They both have a similar flavour but Ceylon cinnamon but your right that it can be slightly sweeter. It also has a different texture (more crumbly) which you may prefer for use in recipes. Chinese cinnamon does have a stronger flavour but some people actually prefer this so it's really just a matter of taste so it's difficult to say whether it's 'worth it'. It can be difficult to get hold of hence it being so expensive. If you're a huge cinnamon fan perhaps purchase yourself a small amount so that you can compare?
The different types of cinnamon are the bark from different types of trees (of the same genus), so naturally, the flavour is a bit different. Which type of cinnamon is more traditional for a particular dish depends on which type of tree grows in that region. It's not so much a case of one being better than the other, but that one might suit the recipe you're preparing better than the other.
Almost all cinnamon available in North America is the "Cassia" cinnamon and it has a spicier flavour, is a darker colour, and when sold in sticks is thick, hard, and forms a loose double-roll shape. "True" cinnamon from Sri Lanka is milder, has a lighter colour, and when sold in sticks is more papery, brittle, and forms a tight single spiral shape.
I recently read that Ceylon cinnamon is also safer because Cassia cinnamon most commonly used can be harmful to the liver if taken in doses over 1 teaspoon a day. One website that spoke about its safety and use is WebMD.
It likely depends on what you're doing with it; most recipes from the U.S. are written for cassia, and it's got more a punch to it than ceylon cinnamon, and in my opinion (it might just be because it's what I'm used to), it holds up better to longer cooking times like what you'd have from baking.
Ceylon desn't have the same sort of heat, but it's not as one-dimensional; it tends to have some almost citrus notes to it.
All that being said, I'm not sure which is the standard in most recipes that call for 'cinnamon' ... I think that south american cooking uses ceylon, not cassia.
I'd say that it's sort of like cold-pressed extra virgin olive oil -- it's good for finishing touches, but it's a waste to substitute it all the time.