What are the main differences between synthetic and dino oil, and is one always better than the other?
A full synthetic oil, as the name states, is "synthesized". By that, they mean it is made in a lab, it is a manufactured product.
Organic (Dino) oil is a product of nature.
So the big difference is the environment in which the oil is made in.
The main selling point on synthetic over organic is because it is manufactured, it is made in a controlled environment. That means far less impurities and a more consistent product.
Organic oil will be influenced by what it was made from, what was in the ground where it was extracted from, etc.
Another way to think about it is synthetic is an additive process. They start with nothing and add in the components they want until they get the end product.
Organic oil is a reductive process, they start with an unrefined product and filter out all the stuff they don't want until they have what they want left.
Though many people do not drive there cars hard enough to need synthetic oils being able to go 10k miles before a change they are cheaper in the long run though more expensive per oil change. And when living in an area where temperatures get below -20 it can really help with starting. Also if care about the environment they are better for it too.
It's not a case of one being unconditionally better than the other, for automobile applications. For example: