Atole is a traditional pre-hispanic drink made with a corn or masa-base. It's creamy and thick. While it can be enjoyed on its own, different flavorings can be added to make other atole flavors like guava, coffee, etc. On the other hand, champurrado is always masa-based. That means you can use atole as a base for it if the atole is made with masa. In terms of consistency and creaminess, though, they're pretty much the same.