The distinction being a hoddie is a sweatshirt with a hood. As opposed to a long sleeve shirt with a hood. Sweatshirts are thicker. Calling it a hoodie would be like calling a long sleeve shirt a swetashirt because they have the same silhouette.
The same distinction between a long sleeve t-shirt and a crewneck sweater. I don't know how they're made, but my layman distinction would be "thickness".