The author states that they believe EventStores are more valuable because they maintain context whereas datomic's records changes without context. Datomic arguably leaves other things out... it doesn't, for example, truly provide an entity kind or a firm consistent schema. It's up to application code to define more formal relationships of data kinds. Arguable you could also say it's up to the application to capture context changes. I do wonder if a hybrid model between these two would result in an overall better solution.